Frequently Asked Questions 
Question #1
What is the difference between the telephone company's ADSL service for high speed access to the Internet and the cable company's CABLE MODEM? Which one is more reliable and better?Answer #1
There are two types of high speed acccess to the Internet: 1)ADSL ADSL is from the telephone company and is called "DSL" for short. This is the short form of the real name which is "Asymmetric Digital Subscriber Line". This technology allows you to use your regular telephone line for high speed access to the Internet, but still allows the use of the same line for normal telephone calling. The maximum connection speed is 1 Megabits per second.(million bits/sec) Whereas, the regular modems can connect at 28,8 ,33,3 and 56,0 Kilobits (thousand bits/sec), depending on what modem you are using. Take into consideration the fact that in reality a 56k modem usually can't achieve much over 45,0 Kilobits/sec because of the bandwidth of the telephone line. So, taking the 56k modem as a comparison to the new DSL modems, we see a difference in speed of about 20 to 1 . Not bad! The cost is about $40. month for the service and $49 for the self install package.($149 if Bell technician has to come and do install) Also, you have a $15 month rental on ADSL modem.(can't buy modem) * Note: You have to live not farther than 4.5 Kilometers from Bell's switching center. The farther you are from the switching center the slower your connection. Cable Modem Cable modem service from the cable company is much faster, with download speeds of 10 Megabits per second maximum. But this is in an ideal world. In reality, cable modems are subject to traffic slowdowns. With cable, all the customers are linked to a continous string much like old christmas tree lights. When usage is high, like around 7 pm at night, which is when a lot of people are home and jumping on the Net, the connection can slow down, just like traffic in rush hour. A real accessment would be around 3 megabits per second. Still about triple the ADSL modems speed. The cost is $40 month for non-subscribers cable TV, and $30 for subscribers. Also, you have to buy or rent cable modem, which is sold at $200 for subscribers and $400 for non-subscribers.(rental $10 subscribers $20 non-subscribers) Also, the truth is, both of these new type of modems rarely achieve this rate of download and the upload is much slower for both technologies. Also, the real slowdown of data transfer, is the Internet itself. When you goto a popular site at a heavy usage time, like 12:00 - 13:00 pm which is lunch hour for millions of workers who surf the net, the connection slows down to a crawl, and it's not because of the modem you are using, it's simply because of the traffic jam on the net.Question #2
I partitioned my old hard drive with the version of FDISK that came with Windows 95. Then I used the SYS command from DOS 6.2 to copy IO.sys and MSDOS.sys to the new drive. Now my Hard drive is corrupted. What's going on here?Answer #2
The way Windows 95's version of FDISK updates the master boot record is different than DOS. The ID values for the primary & extended partition when using DOS's FDISK are 05h and 06h. However, the values when using Win95's version of FDISK are 0eh and 0fh. DOS has no idea what these codes mean and will report these partitions as NON-DOS partitions. If you want to be able to use DOS and WIN95 operating systems on the same computer, use the /X switch with WIN 95 FDISK command when partitioning your hard drive, and your hard drive will be compatible with DOS and WIN95. EX: FDISK /X C:Question #3
I want to be able to use DOS 6.2 and Windows 95 on my computer, but after I installed Windows 95, I can't seem to use Dos as Windows 95 disabled Dos. What can I do to be still able to choose either operating system depending on what I want to do?Answer #3
Here's a great way to create a Dual Boot Win95/98 and Dos system. First, boot up with a DOS floppy system disk in drive A: and then use the ATTRIB -r -s -h command to turn off the READ-ONLY, HIDDEN & SYSTEM attributes of the IO.SYS and MSDOS.SYS files on drive A: type the following: ATTRIB -r -h -s msdos.sys ATTRIB -r -h -s io.sys Then copy those two system files,( io.sys and msdos.sys) to the root directory of the Drive C:\ renamed as MSDOS.DOS and IO.DOS. Also, copy the COMMAND.COM file on A:\ to the root directory of drive C: renamed COMMAND.DOS. Don't forget to reset the attributes of IO.SYS & MSDOS.SYS on drive a: back to ATTRIB +r +h +s msdos.sys ATTRIB +r +h +s io.sys Now, using the ATTRIB command again turn off the attributes of WIN95/98's MSDOS.SYS file.(This file will be in the root directory C:\) ATTRIB -r -s -h msdos.sys NOTE * the MSDOS.SYS file for Win95/98 is a text file and is not the same file as the DOS - MSDOS.SYS file which is a binary system file. Using EDIT, edit the WIN95/98 version of MSDOS.SYS and under the [OPTIONS] section of MSDOS.SYS add the following lines: BootMenu=1 Bootmulti-1 Don't forget to reset the attributes of MSDOS.SYS as the following: ATTRIB +r +s +h msdos.sys Reboot, and from the menu select: Command line Prompt .... to boot to Dos Normal .....to boot to Windows 95 That's it !Question #4
I am considering re-formating my hard drive as I've been having major problems with my Windows 95 operating system as well as with other programs running in Windows. What's the best way to go about this?Answer #4
Caution ! Before you format your hard drive, are you sure that is what you want to do. If you are having problems with Win95, sometimes you can solve a lot of problems just by re-installing Win95. Before you try to re-install Win95 or reformat your drive, you should do a complete backup of your important data and program files using a tape backup system etc. Also, be certain to make a "START UP" floppy disk by going to the START MENU/SETTINGS/CONTROL PANEL/ADD & REMOVE PROGRAMS/STARTUP DISK. Put on this disk or another disk these system files: IO.SYS, MSDOS.SYS, COMMAND.COM, AUTOEXEC.BAT, CONFIG.SYS, SCANDISK.EXE, SYSTEM.DAT, USER.DAT, SYSTEM.INI, WIN.INI, CHKDSK.EXE, MEM.EXE, FDISK.EXE, FORMAT.EXE, SYS.COM, ATTRIB.EXE, EDIT.COM, QBASIC.EXE(used by EDIT.COM), MSCDEX.EXE(needed for CD-ROM), CD-ROM driver(normally loaded in config.sys), and all other drivers normally loaded in config.sys and autoexec.bat.(such as for sound card etc) Then before you re-format your hard drive, be certain to have an old copy of DOS 6.20 on floppies. Also, if your Win95 is only the upgrade version(cheaper) and not the full version on CD , then you are also going to need the old version of Windows 3.1 and have to install that first. The reason you need MSCDEX.exe and your CD-ROM driver files, is quite simple. You can't access the CD-ROM in DOS without first installing these files. If you can't access the CD-ROM, How would you be able to install WIN95 from CD? Also, without the START UP disk you created before formating your hard drive, you wouldn't be able to boot the computer to re-install Windows. Many people have a poor or limited understanding of the complexities of their operating system and setup, and they can therefore fall into the "Technical Pit" way over their heads. It seems to be a human trait to trivialize complex procedures when we are not aware of whats involved. If you are unsure of what you are doing or just not interested in all these complex issues, I suggest you consult a Technician or other technical consultant, and pay them to do it for you. It can save you a lot of grief !Question #5
I've heard a scary tale from a friend about a file called PICTURE.EXE that he got as a email attachment. Apparently, it was a virus that tampered with his system. What's the scoop on this ?Answer #5
If you get an email attachment called "PICTURE.EXE" , delete it right away. This file is not a virus but actually a trojan horse. When you run this executable file, it places two small files on your hard drive, "NOTE.EXE & MANAGER.EXE". Then the program edits your WIN.INI file so that these files will auto launch the next time you boot Windows. These beauties will search your hard drive looking for user names & passwords for AOL etc. and for password protected web sites you belong to. The program then establishes a Internet connection and sends the data to a site in China. No bullshit! The same program goes by the alias's of Backdoor Note & URLSnoop. Good Luck!Question #6
How do I transfer large files from one computer to another in my home without using floppy disks? Both computers have modems.Answer #6
With Interlnk (interlnk.exe & intersvr.exe) that comes included in DOS 6, you can hook up two computers together through their serial ports using a single NUL MODEM cable. The server computer is set up just by typing "C:\DOS\intersvr.exe The client side computer must first be set up by editing the CONFIG.SYS and adding the line: DEVICE=C:\DOS\INTERLNK.EXE Then don't forget to reboot for it to take effect. Then setup the client for file transfer by typing "C:\DOS\interlnk.exe On the server side, the screen will show the following: Microsoft Interlnk Server Version 1.0 This Computer Other Computer (Server) (Client) A: equals D: B: equals E: C: equals F: Transfer | Port=Com2 | Speed=115200 | ALT + F4 =EXIT What this does is redirect the drive letters on the server since the drive letters on the client remain the same. If you want to copy a file on the C:\ drive of the server to the clients C:\ drive you would type this: COPY F:\files\***.** C:\FILES The Server's hard drive would be F:\ and the clients C:\ The Server's A:\ drive becomes D:\ & its B:\ drive becomes E:\ * Note: With INTERSVR running on the server, you cannot use that computer as it becomes the slave of the client. You can end your session by simply typing ALT F4 and resume your normal functions.Question #7
How do I create a short cut to my applications on the desktop of Windows 95?Answer #7
One of the easiest ways to start a favorite application you use often is to create a short cut by Clicking and Dragging the Apps. executable (XXXX.EXE) file to the desktop. You can do this from either My Computer or Windows Explorer in Windows 95/98. Another way is to select the XXX.EXE file, then right click the desktop, and choose " Paste Shortcut..." from the pop up menu. The Desktop's right mouse button menu, also offers a New Shortcut option.Question #8
Can you tell me how to get one of my programs to be listed on the Start Menu of Win95?Answer #8
You can add an Application to the "START" menu by dragging it's Desktop Icon to the "Start" menu. Also, you can do the same by dragging the App's executable file (XXX.EXE) from MY COMPUTER or WINDOWS EXPLORER to the "START" menu. Now you can launch the program with 2 clicks.Question #9
What's this I hear about the "Penpals" Trojan Horse ?Answer #9
If you receive an email from the Internet with the Subject "JOIN THE CREW or PENPALS" delete it immediately ! ** DO NOT OPEN THIS EMAIL ** The letter appears to be a friendly request to become a PENPAL, but by the time you read it, your BOOT SECTOR of your hard drive has already been destroyed. This TROJAN HORSE will automatically self-replicate itself and re-send itself to any email addresses in your email inbox. At present there is no remedy for this TROJAN. So BEWARE !!Question #10
How can I test my computers power supply to see if it's still good?Answer #10
To test a computer's power supply you will need a volt meter, any one will do and they are quite cheap to buy.(RADIO SHACK etc) The power supply of most computers is the most failure prone component inside your computer. The most important thing to understand about computer power supplies is that you have to test them while they are under "LOAD". This means test them while they are still connected to motherboards and drives.( Test them at the back end of the power connectors.) This is the most confusing aspect for "inexperienced" users to grasp. You see the power supply will not generate voltages if it "DETECTS" no load. Then, the unaware person makes the erroneous conclusion that the power supply is DEAD. Costly mistake ! Also, the "BANE" of power supplies is those two pesky "DEVILS" .. "DUST ACCUMULATION" & "OVERHEATING". Inside a computer can get really dusty, as the fan blows constantly, and a frequent vacuuming out is recommended. Dust accumulation on digital chips and circuits cause them to run hotter than normal and therefore result in more failures. If the cheap fan on the power supply stops working properly then the critical cooling of the insides of the computer is seriously affected and overheating ensues. Failure of the Microprocessor and other critical components will follow. Most new systems also have CPU fans that can also fail. The following problems point to the power supply: 1) Power on start up failure, needs repeated switching on. 2) Spontaneous re-booting or intermittent lock-ups. 3) Intermittent memory errors.(weak 5v power to memory) 4) Hard disks fail to spin up.(weak 12 volt supply) 5) Overheating due to power supply fan failure. 6) Bizarre & erratic system behaviour. 7) Electric shocks received from system case. 8) System completely dead. 9) Smoke coming from case. 10) Blown house fuses or circuit breakers. Now, for another point about power supplies.... Any bizarre or erratic system behaviour can be a symptom of possible power supply failure. If the power supply is not meeting the systems demands as far as current is concerned, perhaps because of marginally failing components, then weird system behaviour can appear, such as random memory parity errors at different locations. A valid test procedure is to substitute the power supply with a known good one, if problems cease then that's it. Also, don't try to open the power supply to fix it as there are dangerous internal voltages in these switch mode power supplies. Anyway, they are much too complicated to be worth fixing.Question #11
How do I go about changing my monitors settings in Windows 95 back to their original settings. I tried to set the resolution in Control Panel to 16 bit color, but it seems my monitor can't handle such high resolution. Now all I get is a blank screen with wiggly lines across the middle. I can't even use Windows now to fix the problem. Help!Answer #11
First, you will have to boot in "SAFE MODE" by pressing F8 when you start up your computer. Windows will boot with minimal settings for the display. (16 colors & 640 x 480 resolution) Then, click on "START" ... "CONTROL PANEL" ... "DISPLAY" ... "SETTINGS" . Change your configuration for your monitor then restart Windows. If the new setting you have chosen still doesn't work, repeat the process of rebooting in safe mode and try another setting until you get the highest resolution that your monitor and video card can handle. Sometimes Windows 98 will suggest you upgade your video driver either from CD-ROM, floppy disk or over the Internet. If you are having frequent video problems, you can usually goto the web site of the manufacturer of your video card and download the latest drivers. Check your video card's documentation for a URL of their web site or do a search on Yahoo, Excite etc...Question #12
How can I get Windows 98 to display the filename extensions in Windows Explorer?Answer #12
Start up Windows Explorer, and on the menu bar click on VIEW ... then FOLDER OPTIONS ....then click VIEW ... then unset the check mark in the box titled "Hide File Extensions" Exit and "VOILA" you can now see the file extensions of your files.Question #13
Sometimes when I'm not using my PC for a while, like when I go downstairs to make something to eat for lunch or when I have to tend to other things, my computer goes dead and refuses to work. I tried disabling the screen saver in Windows, thinking that was the problem, but it still happens every now and then. I then have to do a comlete re-boot to get it to work again. Any good guess as to what the problem could be?Answer #13
The Environment Protection Association started a certification program for energy efficient PC's and peripherals a few years ago, called the "ENERGY STAR" program. For a PC to conform to these specifications it must drop to a minimum power draw of 30 watts or less during periods of inactivity. If your system conforms to these specifications you will see an "ENERGY Star" logo displayed at boot up. The problem with these systems is that the motherboard and drives can literally go to "SLEEP" or standby mode when inactive for long periods, so as to conserve power. This low power consumption mode sometimes causes the power supply to not function properly, perceive inaccurately a "NO LOAD" condition and thus automaticly shut down. Solution: Try first to disable power conservation options in the BIOS setup on boot up. Also, disable any power management features in Windows. If, that doesn't solve your problem, I suggest you change the power supply, as they are very inexpensive and easy to replace as a unit. Also, make sure the new power supply has a LOW minimal load specification.Question #14
I'm having extreme problems installing Windows 98 from the CD-ROM that I bought. My system keeps crashing or hanging when I try to do the install. I've tried to do it from Win95 and from plain old DOS 6.2, but no luck. What can I do to solve this head ache?Answer #14
Well I can't give you any simple 2 step solution to your problem, especially since you have provided very limited information about your system, configuration, hardware, operating system etc. But, what I can give you is a verbatim copy of a trouble shooting text file from Microsoft's Win98 startup disk. It's very informative. Here it is: What's New for the Windows 98 Startup Disk? The Startup Disk has changed significantly for Windows 98. The following items are new for Windows 98. - MULTI-CONFIG START MENU - REAL-MODE CD-ROM DRIVERS - EBD.CAB FILE - RAMDRIVE - WINDOWS 98 STARTUP PROBLEMS - USING THE TOOLS AVAILABLE ON THE STARTUP DISK MULTI-CONFIG START MENU ======================= If you boot your computer using the new Windows 98 Startup Disk, a boot menu appears allowing you the option to load drivers for the most common CD-Rom drives or perform a normal clean boot. After you make your selection, the Config.sys file loads the appropriate CD-ROM driver (if selected) and then loads a 2MB RAMDrive. The RAMDrive is used to store all the diagnostic tools necessary to troubleshoot the most common problems. NOTE: The RAMdrive may cause your CD-Rom to pushed back 1 drive letter. If your CD-Rom is usually drive D:, it will now be Drive E:. REAL-MODE CD-ROM SUPPORT ======================== The Windows 98 Statup Disk includes generic ATAPI IDE & SCSI CD-ROM drivers that allow your CD-ROM to function at Dos when the Windows 98 GUI is not available. NOTE: Not all CD-Rom drives are supported. If your CD-Rom drive does not function with these drivers, you must use the drivers that came with your CD-Rom drive. EBD.CAB FILE ============ The Ebd.cab file is a compressed file whose contents are extracted to the Ramdrive during the startup process. The table below identifies the files in the Ebd.cab file. File Function Attrib.exe Add or remove file attributes Chkdsk.exe A simpler and smaller disk status tool Debug.exe Debugging utility Edit.com Real-mode emergency text editor Ext.exe New, simple file extract utility Format.com Disk format tool Mscdex.exe Microsoft CD-ROM file extension for MS-DOS Scandisk.exe Disk status tool Scandisk.ini Disk status tool configuration file Sys.com Transfers system files and make disk bootable Uninstal.exe A tool to remove Windows 98 from the system and return the system to its previous state CREATING A RAMDRIVE =================== The RAMDrive is created during the processing of the Config.sys file and is 2MB in size. The Ramdrive is created using system RAM to emulate a physical Hard Disk. Without creating the RAMdrive, we would not have enough space on a single 1.44 meg floppy disk to contain all the diagnostic tools as well as the CD-Rom drivers. WARNING: Since the RAMDrive is created during the processing of the Config.sys file and uses System RAM, it is only temporary. It will disappear if you restart your computer normally. LIST OF ALL COMPONENTS ON THE EBD ================================= The following table describes the function of each file copied to the EBD. File Function Aspi2dos.sys Real-Mode Adaptec CD-ROM driver Aspi4dos.sys Real-Mode Adaptec CD-ROM driver Aspi8dos.sys Real-Mode Adaptec CD-ROM driver Aspi8u2.sys Real-Mode Adaptec CD-ROM driver Aspicd.sys Real-Mode Adaptec CD-ROM driver Autoexec.bat Startup batch file Btcdrom.sys Mylex/BusLogic CD-ROM driver Btdosm.sys Mylex/BusLogic CD-ROM driver Command.com Command interpreter Config.sys Loads the device drivers Drvspace.bin Microsoft DriveSpace compression driver Ebd.cab Cab file containing extract utilities Ebd.sys File identifying the ESD Extract.exe File to expand the Ebd.cab file Fdisk.exe Disk partition tool Findramd.exe Utility to find the RAMDrive during startup Flashpt.sys Mylex/BusLogic CD-ROM driver Himem.sys XMS Memory Manager Io.sys System boot file Msdos.sys Boot option information (paths, multiboot, and so on) Oakcdrom.sys Generic device driver for ATAPI CD-ROM drives Ramdrive.sys Creates a Ramdrive during startup Setramd.bat Searches for first available drive to be a Ramdrive WINDOWS 98 STARTUP PROBLEMS =========================== This section includes some common troubleshooting steps that can be used when it's necessary to use the Windows 98 Startup Disk. These steps are designed to get the user at least into Safe-Mode where you have access to Windows 98 extensive HELP system to further troubleshoot any issues. Starting Your Computer in Safe Mode ----------------------------------- There are several reasons why Windows 98 may fail to start properly. The first step in troubleshooting is to try starting your computer in Safe Mode. If Safe Mode works, you can then use the extensive Help system and troubleshooters located in the Start menu/Help option. >>>To start your computer in Safe Mode: 1. Remove the Startup Disk and restart your computer. After the computer restarts but before Windows begins to load, hold down the CTRL key until the Microsoft Windows 98 Startup Menu appears. (If you are running Windows 95, press the F8 key at the "Starting Windows 95" prompt.) 2. From the Startup menu, select Safe Mode. If you can start your computer in Safe Mode, use Windows 98 Help to resolve your original issue. Setup Fails and the Computer Will Not Start ------------------------------------------- There are a few common reasons why Windows 98 Setup may fail to complete successfully. The following section explains what you can do to recover from these situations. For more information on other Setup problems, see the Setup.txt file in the Win98 folder of your Windows 98 CD or Setup Disk #1. If you encounter any of these error messages while running Setup: * Invalid System Disk * Incorrect MS-DOS Version * Missing or Corrupted Command.com * Compression Driver errors It is likely that your computer's startup drive may need updated system files. You can use the SYS command to copy the needed files to your computer. NOTE: If you are currently loading compression software, you will need to know your host drive letter. This is typically H. If you are not loading any compression software, then you will need to SYS your C drive. >>>To use the SYS command to copy system files to your computer: 1. Restart your computer using the Windows 98 Startup Disk, select option 2 on the Startup menu, and then press ENTER. 2. At the A:\ prompt, type: SYS X: (where X is your Host or Startup drive). 3. If the procedure is successful, a "System transferred" message appears. If it is not successful, check to be sure you are typing the correct drive letter for your Host Drive. IMPORTANT: If you have installed software that came with your hard drive, be sure to read the documentation that describes how to start your computer using a floppy disk. Antivirus Software ------------------- If antivirus programs are left running during Setup, they may prevent Setup from properly updating the system files. If this occurs, disable or uninstall the antivirus program, and then run Setup again. NOTE: Some computers have built-in antivirus software. This built-in software should also be disabled before running Setup. If the software is left enabled, you may receive a warning message informing you that the Master Boot Record has changed. If you see such a message, you MUST accept these changes or Setup may stop responding. Setup Stops Responding During Hardware Detection ------------------------------------------------ If Setup stops responding while it is detecting the hardware in your computer, turn your computer off and wait a few seconds, then turn it back on. You may need to do this several times, because Setup could stop responding during several different detection modules. NOTE: Use the power switch to turn your computer completely off. Do not use the reset button or press CTRL+ALT+DELETE to restart your computer. If Setup still fails to complete successfully, it may be necessary to start your computer in Safe Mode so that you can view the Help topics associated with hardware detection. Compressed Drives Not Mounted ----------------------------- There are several reasons why compressed drives may not be accessible. If your Windows directory is on a compressed drive that is not mounted, you will not be able to start Windows. If you suspect problems with your compressed drives, try using Scandisk to fix them. From the A:\ prompt, type: Scandisk /Mount X: where X is the drive letter of the compressed drive. ScanDisk will then attempt to repair any errors and mount the drive. If there is not enough memory to check your compressed drives, see "Installing Windows 98 from MS-DOS," in the Setup.txt file on Setup Disk 1 or the Windows 98 CD. USING THE TOOLS AVAILABLE ON THE STARTUP DISK ============================================= This section decribes how to use some of the utilities included with the Windows 98 Startup Disk. To run each program you should do the following: 1. Put the Windows 98 Startup Disk in the floppy disk drive, and then restart your computer. 2. At the Startup menu, select option 1 or 2 (depending upon whether you need CD-ROM access), and then press ENTER. 3. At the MS-DOS command prompt (A:\), type the name of the utility you wish to run, and then press ENTER. SCANDISK.EXE and CHKDSK.EXE ---------------------------- These two programs are useful for checking your hard disk for errors. If you suspect there may be file corruption or other problems with your hard disk(s), run ScanDisk to check for and repair errors. To check all your hard disks for errors, type: Scandisk /all To perform a full surface scan of your hard disk(s) for maximum protection against data loss, type: Scandisk /all /Surface NOTE: You may receive errors about Long File Names. The MS-DOS version of ScanDisk can only detect problems with long file names, it cannot fix them. To correct these types of errors, you must run ScanDisk from within Windows 98. NOTE: If you have any compressed drives, you may receive an error message stating that there is not enough memory to check your compressed drives. To solve this problem, try starting your computer with the Windows 98 Startup Disk, as described in Step 1, earlier in this section. Select option 2. This may allow ScanDisk enough memory to check your compressed drives. If ScanDisk is unable to check your drives, try using CHKDSK.EXE instead. CHKDSK will check for cross-linked files and lost allocation units. SYS.COM ======= The SYS command is used to copy system files from one disk to another. Your computer needs these system files to start. >>>To SYS your C drive, type: SYS C: and then press ENTER. After a few seconds, a "System Transferred" message appears. The following files are copied to your hard disk during the SYS procedure: * IO.SYS * MSDOS.SYS * COMMAND.COM If the SYS C: command does not work and you have a compressed drive, you may need to type the drive letter of your host drive. With the DblSpace or DrvSpace programs, the host drive is typically designated drive H. If you are not sure of the drive letter, run ScanDisk and see if it prompts you about your compressed drive. FDISK.EXE and FORMAT.EXE ------------------------ FDISK and FORMAT are utilities necessary for installing a new hard disk in your computer or for starting over fresh with a clean disk. FDISK is used first to create a partition and then FORMAT is used to make the partition available for use. WARNING: Using FDISK incorrectly can destroy all data on your hard disk. If you are unsure of how to use FDISK, consult your computer documentation. You can use the Windows 98 version of FDISK to create FAT32 partitions on drives over 512 megabytes in size. FAT32 reduces the cluster size for large drives and allows you to create single partitions on drives over 2 GB. To view your current drive status, type FDISK /STATUS at the MS-DOS command prompt. After you have partitioned a drive using FDISK, you will need to use the FORMAT command. To format a newly partitioned drive, type: FORMAT X: Where X represents the letter of the drive that you want to format. If you want to format drive C, you need to make this disk a system disk so that your computer can start. To do this, type /s at the end of the FORMAT command. For example: FORMAT C: /s System Startup files will be automatically copied after your drive is formatted. CD-ROM Drivers -------------- The Windows 98 Startup Disk includes a set of generic CD-ROM drivers. These drivers work with most IDE ATAPI and SCSI CD-ROM models. If your particular CD-ROM drive does not work with these drivers, you will need to use the drivers that came with your CD-ROM drive. Following are some known issues about the CD-ROM drivers: 1. CD-ROM drives connected to sound cards may not work properly. 2. Early proprietary CD-ROM drives (for example, Mitsumi, Panasonic, Sony) may not work with these drivers. Some older IDE controllers may fail as well. 3. The SCSI drivers on the Startup Disk support most Adaptec, Buslogic, and Mylex adapters. Some other SCSI CD-ROM drives may not work with the drivers on the Startup Disk. 4. If your SCSI controller is configured for a non-default I/O range, the drivers may not detect your SCSI card. Consult your SCSI driver documentation for the default I/O ranges for your card. 5. Drivers are not included for any PC Card (PCMCIA) CD-ROM drives. UNINSTAL.EXE ------------ If you need to remove Windows 98 from your system, you can use the real-mode uninstall utility included on the Windows 98 Startup Disk. IMPORTANT: If you did not choose the option to "Save System Files" during Setup, then you will be unable to use this utility. >>>To use the uninstall utility, perform the following steps: 1. Restart your computer with the Windows 98 Startup Disk, select option 2, and then press ENTER. 2. At the MS-DOS command prompt, type UNINSTAL, and then press ENTER. NOTE: If you see the message "WINUNDO.DAT is missing or corrupt," you cannot uninstall this version of Windows 98. EXT.EXE ------- The EXT command is used in conjunction with the Extract.exe utility to make it easier to extract Windows 98 files to your hard disk. You can use this to replace missing or damaged files. This utility is extremely useful if you are receiving errors during startup about missing files, or execution errors such as General Protection Faults or invalid page faults. >>>To use Ext.exe to extract a file, perform the following steps: 1. Use the Startup Disk to start your computer. Select option 1, and then press ENTER. 2. Make sure the Windows 98 CD is inserted in the drive. 3. Type EXT at the MS-DOS command prompt, and then press ENTER. 4. Follow the prompts to indicate the location of the Windows 98 Setup files, the files you wish to extract, and the location in which you want to place the extracted files. NOTE: If your CD-ROM drive letter is E, then type the location to the Setup files as E:\WIN98. NOTE: If you wish to extract more than one file at a time, you can use wild card characters.Question #15
I can't get Windows 98 to boot up. I keep getting "Protection Error" & "Fatal Exception Error" Messages. Also, when I choose to boot in "Safe Mode" by pressing "Control Key" or F8, It seems to want to boot but when "HIMEM.SYS" is checking memory, I get a "MEMORY ERROR AT #XXXX:xxxxx " or whatever. The computer boots perfectly in DOS mode. I've tried to re-install Win98 , but the install keeps hanging. What is the problem here?Answer #15
It would appear that you could have a partially failed memory module. Sometimes, these modules can have only a few of their millions of transitors fail without warning. Usually due to heat. In DOS mode , you are only using the first 640 kbytes of memory. So, if the failed spot in memory is way above this location, it might not show up in the POST ( Power On Self Test) at BOOT UP. Where as, HIMEM.SYS checks memory more thoroughly, and that could be why the HIMEM sees the problem memory when you are trying to load Win98 in "SAFE MODE". Try to replace or substitute a known good memory module with the one presently in your computer. This method of "SUBBING" in a known good memory module is a valid test procedure, used often by technicians. If your system works OK after, then you have found the problem. Also, try pressing F8 to get the Windows startup menu and then choose the LOGGED option. This way Windows will record every step it takes during the BOOT UP process in a file in the root directory called BOOTLOG.TXT. Then reboot Windows in SAFE mode and use a text editor to look at the BOOTLOG.TXT file. Look for a "fail" line in the BOOTLOG.TXT file, as this can often give excellent clues as to the cause of the problem.Question #16
How does a normal Laser Printer work, as I am curious and want to understand the functions of the mechanism so as to be able to solve any simple problems that might creep up?Answer #16
Here is the process of the Canon & Xerox Electrophotographic Laser printers. Hp Laser Jets are slightly different. 1) The 1st step in the EP process is the CHARGING step. A special wire called the "CHARGING CORONA WIRE" gets negative 600vdc charge from the High Voltage Power Supply.(HVPS) This wire is in the EP toner cartridge above the photosensitive drum. This ends up charging the photosensitive drum to -600vdc. 2) Next is the EXPOSURE step. The laser turns on and scans the photosensitive drum from side to side, turning on and off, writing the BITS of information that the printer controller sends it. The spots where the laser turns on and touches the drum ( which is at a potential of -600vdc ) are reduced to -100vdc. (0 vdc in the HP) As the drum rotates, a pattern of the text to be printed is formed on the drum. At this point the printer controller sends a signal to the paper roller to feed a sheet of paper, where it stops at the registration rollers. 3) Now its the DEVELOPING step. In this step, toner is transferred to the areas on the EP drum that were exposed to the laser. Another roller called the DEVELOPING ROLLER is charged to a -600vdc and the toner sticks to this roller due to the combined effect of a magnet inside it and the electrostatic charge between the toner and roller. When the developing roller which is covered in toner rolls against the EP drum, toner is attracted to the areas that have been exposed by the laser, as they are at a lesser potential of -100vdc (0vdc Hp). The photosensitive drum now has toner stuck to it at the spots that were written to it by the laser. The developed image is ready to be transferred to the paper in the next step. 4) This is the TRANSFER step . The controller tells the registration rollers that the paper should be fed under the photosensitive drum and the transfer begins. The controller turns on the CORONA WIRE (roller in HP Laserjet) , which transfers a +600vdc charge to the paper. The paper thus charged, pulls the toner from the photosensitive drum onto the paper, because the paper and toner have opposite charges. Once past the corona wire, the paper comes into contact with the static-eliminator strip, which elimanates all charge on the paper. Note: If the Static-eliminator did not bleed this charge away, the paper would get attracted to the drum and cause a paper jam. The toner is held to the paper by a weak electrostatic charge and will be made permanent by the next FUSING step. 5) The FUSING step. Once the fusing roller and pressure roller get the paper, the FUSER which is at 350 degrees F, melts the polyester resin of the toner and the the pressure roller presses it permanently into the paper. The paper exits the FUSER assembly and exits the printer. As the paper exits the printer, it trips a sensor, which tells the printer to finish up the process with the CLEANING step. 6) CLEANING step. Here the printer cleans up after itself. A rubber blade inside the cartridge scraps any unused toner from the DEVELOPING roller into a used toner receptacle inside the cartridge. Also, a fluorescent lamp discharges any remaining charge on the photosensitive drum. NOTE: If the fluorescent burns out and you no longer have cleaning of the drum, you will get ghost of your old images on your new ones.Question #17
I frequently have a problem with my Canon Bubble Jet printer running out of ink. I'm sure that the cartridge can't be empty as quickly as it appears, but I have to frequently replace the ink cartridge. These can cost $25 each time and gets to be expensive. Do you have any good suggestions?Answer #17
You can try refilling those used ink jet cartridges with kits available at computer supply stores, but it can be a bit of a messy job. Also, computer tech purists do not agree with ink re-fills, they say that the ink inside these refills is poorer quality and can result in poor printer performance. Also, the print head is included in the cartridge and is changed each time the cartridge is replaced, which is a good thing. Still, a refill is a cheaper solution for most people who print a lot. Also, your ink jet's cartridge may be just drying out. The ink will dry in those small nozzles if you don't use the printer at least once a week. Here's a trick that technies use often: If the printer was previously printing fine and then just puts out blank pages do the following. Take out the ink cartridge and then using a paper towel moistened with window cleaner(Windex etc), tap the print head lightly a couple of times. Re-insert the cartridge back in the printer and it should print again. Of course this will only work if the pin holes are only blocked with dry ink. It won't work if the cartridge is empty.Question #18
I'm thinking of buying a new computer and would like advice on where to go to get the best price, best quality and the best warranty ? What place gives the best quality service on repairs for their customers?Answer #18
Asking "Where do you go to buy the best computer?" is like asking "Where do you go to buy the best automobile?" It's a matter of opion. Who knows ! As usual, you usually get what you pay for, when buying a computer. If you buy from a well known name brand like IBM, Compaq, Hewlett Packard, ETC.. you usually get good quality products with good quality after sale service and warranty coverage. But you also get the higher price tag. Lesser known "CLONES" can still be a good buy if they are assembled with good quality components, such as Brand name motherboards, drives, CD-ROMS, video cards, and sound cards etc. These systems can be quite a bit cheaper on initial price and you can save yourself some money. The problem with "CLONES" is that sometimes the PC assembler uses cheaper components so as to remain profitable while offering the lowest possible prices to the customer. Also, the after sale warranty and repair service can be rather poor. There is no way the store can sell you a computer at rock bottom prices and still offer their customers great warranty service. They may make all kinds of wonderful claims about 2 year warranty etc, but as soon as you have a real problem, you will find that most of these wonderful warranties are actually with the manufacturer of the failed component and not the responsibility of the store that sold you the PC. The store will send out the failed component to the manufacturer to be repaired or replaced . This can be a time consuming process and long waits for the customer are the norm. Other factors in choosing a good computer, at a good price, are the following: How NEW is the computer and its internal components. A lot of "NEWUSERS" are not well informed about the newest technology available. They are often not aware that "Last Years" computer is quite old as far as computers are concerned. I like to use the analogy that 1 year in the computers lifespan is equivalent to 10 years in the lifespan of a automobile. Of course you can get real good deals on last years technology in computers, and getting a Pentium ll instead of a Pentium lll, may be all the computer you may need, depending on what you plan to use it for. If you just want to surf the NET and let the kids play a few video games, then perhaps a Pentium 333 Celeron may be all you need. At last. talk to computer-literate friends or co-workers as they may be your best bet as far as advice is concerned.Question #19
Sometimes when I turn my computer on, it doesn't power up. No lights, no fan operation, no drive lights, nothing. If I switch it on and off a number of times, it will eventually come on, but, this is very irritating for me. Once it comes on it will stay on as long as I'm using it. Is there a problem with the power supply etc?Answer #19
O.K. An irratic power supply it would seem ! Could be a number of things causing this problem and we will start with checking the Power plug to the wall. Is it loose! Check also the AC power cord connected to the back of computer, they can work loose. Try swapping the AC cord. Then open your computer case and check the white power plugs that bring power to the mother board from the power supply , are they loose. Next, while you have the case open,use a DC meter to check the DC voltages on the white power plug to the mother board. Just insert the meters probes into the back end of the plug with the black (negative) touching the back of the black wires of the power plug and the red (positive) probe to the back of the others. You should get 2 voltages, 5 volts DC and 12 volts DC. ( NOTE ** the plug has to be connected to a load (motherboard) in order to get a reading.) If you get good voltages here then power is being supplied to the motherboard, drives, & circuits. Next posibility is a defective power switch on the power supply, sometimes you can replace these cheap switches. If all this fails to solve your problem, try changing the power supply with a good one.Question #20
I'm looking to buy a new computer but I am a bit confused about all the components available,the jargon and hype. Should I buy a computer with a CD-ROM or a DVD player? It seems CD-ROM's come as standard option but that DVD's are an expensive option.Answer #20
Well, it depends on what you plan to do with your new computer and how much you want to spend. DVD disks hold from 5-17 Gigabytes of data, which explains their use for video's and huge games. CD-ROM's can hold only 650 Megabytes of data and is an earlier technology used for the distribution of games and software. Note that you may also read CD-ROM's with a DVD. A good use for DVD is if you like to watch movies on your computer. Also, some of the newer games are stored on DVD's as there is much more room for their enormous program code. One last point is the versatility of the recordable type of CD-ROM's. These type are excellent as a back up medium and also good if you want to make your own CDROM disks, for distributing software for example.Question #21
What's the scoop on this new worm/virus called Explore.zip that we are hearing all kinds of SCARY stories about? Is this as real a threat as most people are suggesting? How can we check our systems to see if we are infected and what are the solutions to possible infection?Answer #21
Well, let's see. I will not give you my own interpretation of whats going on with this virus. Instead, I will give you the most articulate, accurate information available from the people who ARE real experts in this stuff, The Computer Emergency Response Team from Carnegie Mellon University. Information Follows .... Source: CERT/CC Note: The CERT Coordination Center has discovered new information regarding the ExploreZip worm. This re-issue of CERT Advisory CA-99-06 contains new information regarding an additional means by which the Worm can spread, and a caution about disinfecting your systems. We will continue to update this advisory as new information is discovered. We encourage you to check our web site frequently for any new information. Systems Affected * Machines running Windows 95, Windows 98, or Windows NT. * Machines with filesystems and/or shares that are writable by a user of an infected system. * Any mail handling system could experience performance problems or a denial of service as a result of the propagation of this Trojan horse program. Overview The CERT Coordination Center continues to receive reports and inquiries regarding various forms of malicious executable files that are propagated as file attachments in electronic mail. During the second week of June 1999, the CERT/CC began receiving reports of sites affected by ExploreZip, a Trojan horse/worm program that affects Windows systems and has propagated in e-mail attachments. The number and variety of reports we have received indicate that this has the potential to be a widespread attack affecting a variety of sites. I. Description Our original analysis indicated that the ExploreZip program is a Trojan horse, since it initially requires a victim to open or run an e-mail attachment in order for the program to install a copy of itself and enable further propagation. Further analysis has shown that, once installed, the program may also behave as a worm, and it may be able to propagate itself, without any human interaction, to other networked machines that have certain writable shares. The ExploreZip Trojan horse has been propagated between users in the form of e-mail messages containing an attached file named zipped_files.exe. Some e-mail programs may display this attachment with a "WinZip" icon. The body of the e-mail message usually appears to come from a known e-mail correspondent, and typically contains the following text: I received your email and I shall send you a reply ASAP. Till then, take a look at the attached zipped docs. The subject line of the message may not be predictable and may appear to be sent in reply to previous e-mail. Opening the zipped_files.exe file causes the program to execute. It is possible under some mailer configurations that a user might automatically open a malicious file received in the form of an e-mail attachment. When the program is run, an error message is displayed: Cannot open file: it does not appear to be a valid archive. If this file is part of a ZIP format backup set, insert the last disk of the backup set and try again. Please press F1 for help. Destruction of files * The program searches local and networked drives (drive letters C through Z) for specific file types and attempts to erase the contents of the files, leaving a zero byte file. The targets may include Microsoft Office files, such as .doc, .xls, and .ppt, and various source code files, such as .c, .cpp, .h, and .asm. * The program may also be able to delete files that are writable to it via SMB/CIFS file sharing. The program appears to look through the network neighborhood and delete any files that are shared and writable, even if those shares are not mapped to networked drives on the infected computer. * The program appears to continually delete the contents of targeted files on any mapped networked drives. The program does not appear to delete files with the "hidden" or "system" attribute, regardless of their extension. System modifications * The zipped_files.exe program creates a copy of itself in a file called explore.exe in the following location(s): On Windows 98 - C:\WINDOWS\SYSTEM\Explore.exe On Windows NT - C:\WINNT\System32\Explore.exe This explore.exe file is an identical copy of the zipped_files.exe Trojan horse, and the file size is 210432 bytes. MD5 (Explore.exe) = 0e10993050e5ed199e90f7372259e44b * On Windows 98 systems, the zipped_files.exe program creates an entry in the WIN.INI file: run=C:\WINDOWS\SYSTEM\Explore.exe On Windows NT systems, an entry is made in the system registry: [HKEY_CURRENT_USER\Software\Microsoft\Windows NT\CurrentVersion\Windows] run = "C:\WINNT\System32\Explore.exe" Propagation via file sharing Once explore.exe is running, it takes the following steps to propagate to other systems via file sharing: * Each time the program is executed, the program will search the network for all shares that contain a WIN.INI file with a valid "[windows]" section in the file. * For each such share that it finds, the program will attempt to + copy itself to a file named _setup.exe on that share + modify the WIN.INI file on that share by adding the entry "run=_setup.exe" The account running the program on the original infected machine needs to have permission to write to the second victim's shared directory. (That is, no vulnerabilities are being exploited in order for the program to spread in this manner.) The _setup.exe file is identical to the zipped_files.exe and explore.exe files on the original infected machine. * The original infected system will continue to scan shares that have been mapped to a local drive letter containing a valid WIN.INI file. For each such share that is found, the program will "re-infect" the victim system as described above. On Windows 98 systems that have a "run=_setup.exe" entry in the WIN.INI file (as described previously), the C:\WINDOWS\_setup.exe program is executed automatically whenever a user logs in. On Windows NT systems, a "run=_setup.exe" entry in the WIN.INI file does not appear to cause the program to be executed automatically. When run as _setup.exe, the program will attempt to * make another copy of itself in C:\WINDOWS\SYSTEM\Explore.exe * modify the WIN.INI file again by replacing the "run=_setup.exe" entry with "run=C:\WINDOWS\SYSTEM\Explore.exe" Note that when the program is run as _setup.exe, it configures the system to later run as explore.exe. But when run as explore.exe, it attempts to infect shares with valid WIN.INI files by configuring those files to run _setup.exe. Since this infection process includes local shares, affected systems may exhibit a "ping pong" behavior in which the infected host alternates between the two states. Propagation via e-mail The program propagates by replying to any new e-mail that is received by the infected computer. The reply messages are similar to the original e-mail described above, each containing another copy of the zipped_files.exe attachment. We will continue to update this advisory with more specific information as we are able to confirm details. Please check the CERT/CC web site for the current version containing a complete revision history. II. Impact * Users who execute the zipped_files.exe Trojan horse will infect the host system, potentially causing targeted files to be destroyed. * Users who execute the Trojan horse may also infect other networked systems that have writable shares. * Because of the large amount of network traffic generated by infected machines, network performance may suffer. * Indirectly, this Trojan horse could cause a denial of service on mail servers. Several large sites have reported performance problems with their mail servers as a result of the propagation of this Trojan horse. III. Solution Use virus scanners While many anti-virus products are able to detect and remove the executables locally, because of the continuous re-infection process, simply removing all copies of the program from an infected system may leave your system open to re-infection at a later time, perhaps immediately. To prevent re-infection, you must not serve any shares containing a WIN.INI file to any potentially infected machines. If you share files with everyone in your domain, then you must disable shares with WIN.INI files until every machine on your network has been disinfected. In order to detect and clean current viruses, you must keep your scanning tools up to date with the latest definition files. Please see the following anti-virus vendor resources for more information about the characteristics and removal techniques for the malicious file known as ExploreZip. Aladdin Knowledge Systems, Inc. http://www.esafe.com/vcenter/explore.html Central Command http://www.avp.com/zippedfiles/zippedfiles.html Command Software Systems, Inc http://www.commandcom.com/html/virus/explorezip.html Computer Associates http://www.cai.com/virusinfo/virusalert.htm Data Fellows http://www.datafellows.com/news/pr/eng/19990610.htm McAfee, Inc. (a Network Associates company) http://www.mcafee.com/viruses/explorezip/default.asp Network Associates Incorporated http://www.avertlabs.com/public/datafiles/valerts/vinfo/va10185 .asp Sophos, Incorporated http://www.sophos.com/downloads/ide/index.html#explorez Symantec http://www.symantec.com/avcenter/venc/data/worm.explore.zip.htm l Trend Micro Incorporated http://www.antivirus.com/vinfo/alerts.htm Additional sources of virus information are listed at http://www.cert.org/other_sources/viruses.html Additional suggestions * Blocking Netbios traffic at your network border may help prevent propagation via shares from outside your network perimeter. * Disable file serving on workstations. You will not be able to share your files with other computers, but you will be able to browse and get files from servers. This will prevent your workstation from being infected via file sharing propagation. * Maintain a regular, off-line, backup cycle. General protection from e-mail Trojan horses and viruses Some previous examples of malicious files known to have propagated through electronic mail include * False upgrade to Internet Explorer - discussed in CA-99-02 http://www.cert.org/advisories/CA-99-02-Trojan-Horses.html * Melissa macro virus - discussed in CA-99-04 http://www.cert.org/advisories/CA-99-04-Melissa-Macro-Virus.html * Happy99.exe Trojan Horse - discussed in IN-99-02 http://www.cert.org/incident_notes/IN-99-02.html * CIH/Chernobyl virus - discussed in IN-99-03 http://www.cert.org/incident_notes/IN-99-03.html In each of the above cases, the effects of the malicious file are activated only when the file in question is executed. Social engineering is typically employed to trick a recipient into executing the malicious file. Some of the social engineering techniques we have seen used include * Making false claims that a file attachment contains a software patch or update * Implying or using entertaining content to entice a user into executing a malicious file * Using e-mail delivery techniques which cause the message to appear to have come from a familiar or trusted source * Packaging malicious files in deceptively familiar ways (e.g., use of familiar but deceptive program icons or file names) The best advice with regard to malicious files is to avoid executing them in the first place. CERT advisory CA-99-02 discusses Trojan horses and offers suggestions to avoid them (please see Section V). http://www.cert.org/advisories/CA-99-02-Trojan-Horses.html ______________________________________________________________________ This document is available from: http://www.cert.org/advisories/CA-99-06-explorezip.html. ______________________________________________________________________ CERT/CC Contact Information E-mail: cert@cert.org Phone: +1 412-268-7090 (24-hour hotline) Fax: +1 412-268-6989 Postal address: CERT Coordination Center Software Engineering Institute Carnegie Mellon University Pittsburgh PA 15213-3890 U.S.A. CERT personnel answer the hotline 08:00-20:00 EST(GMT-5) / EDT(GMT-4) Monday through Friday; they are on call for emergencies during other hours, on U.S. holidays, and on weekends. Using encryption We strongly urge you to encrypt sensitive information sent by e-mail. Our public PGP key is available from http://www.cert.org/CERT_PGP.key. If you prefer to use DES, please call the CERT hotline for more information. Getting security information CERT publications and other security information are available from our web site http://www.cert.org/. To be added to our mailing list for advisories and bulletins, send e-mail to cert-advisory-request@cert.org and include SUBSCRIBE your-e-mail-address in the subject of your message. Copyright 1999 Carnegie Mellon University. Conditions for use, disclaimers, and sponsorship information can be found in http://www.cert.org/legal_stuff.html. * "CERT" and "CERT Coordination Center" are registered in the U.S. Patent and Trademark Office ______________________________________________________________________ NO WARRANTY Any material furnished by Carnegie Mellon University and the Software Engineering Institute is furnished on an "as is" basis. Carnegie Mellon University makes no warranties of any kind, either expressed or implied as to any matter including, but not limited to, warranty of fitness for a particular purpose or merchantability, exclusivity or results obtained from use of the material. Carnegie Mellon University does not make any warranty of any kind with respect to freedom from patent, trademark, or copyright infringement. Revision History June 10, 1999: Initial release June 11, 1999: Added information about the appearance of the attached file Added information from Aladdin Knowledge Systems, Inc. June 14, 1999: Added information about the program's self-propagation via networked shares; also updated anti-virus vendor URLsQuestion #22
While using the Internet and its resources, I read all kinds of things about 56KFLEX, X2, V.90, ADSL, DTE, DCE, Baud, Bits etc. What does all this lingo mean, as I get quite confused with the terminology and was wondering if there was an easier way to learn all these mumble jumble terms?Answer #22
Rather than give you my limited knowledge about Modems and Communications terms and definitions, I've included an excellent treatise on the subject written by Craig Ford, Moderator of the Fidonet Communications Echo.(forum) *************************************************************************** Fidonet COMM Echo Primer For newcomers to this, the FidoNet International echo COMM, there follows a discussion of terms which will be encountered frequently in the messages herein. A firm grounding in these will add considerable to understanding the messages in this echo. +========+ +========+ |Computer| DTE- DCE- DTE- |Computer| | A | Rate +--A--+ Rate +--B--+ Rate | B | | |~~~~~~~~~~|Modem|~~~~~~~~~~~~~|Modem|~~~~~~~~~~| | +========+ +=====+ +=====+ +========+ Pictured above is a brief sketch of a complete signal circuit, consisting of two computers (A & B) interconnected thru their Modems. DEFINITIONS: 56Kbps Modems [Pre-V.90] - Rockwell, USR, Lucent Technologies, and Motorola marketed incompatible chipsets/modems that operated in a server/client format at up to 56Kbps over standard telephone lines prior to the adoption of ITU-T V.90. USR implemented a protocol dubbed X2, and the remainder combined efforts to implement a protocol dubbed K56Flex (a combination of Rockwell's K56Plus and Lucent's VFlex/2 protocols). The X2 and K56Flex protocols do not interoperate. ADSL (Asymmetric Digital Subscriber Line) - a modem technology that converts existing twisted-pair telephone lines into access paths for multimedia and high speed data communications. ADSL transmits more than 6Mbps to a subscriber, and as much as 640 kbps more in both directions. An ADSL circuit connects an ADSL modem on each end of a twisted-pair phone line, creating three information channels; a high speed downstream channel, a medium speed duplex channel, and a POTS (Plain Old Telephone Service) channel. The POTS channel is split off from the digital modem by filters, thus guaranteeing uninterrupted POTS, even if ADSL fails. The high speed channel ranges from 1.5 to 6.1 Mbps, while duplex rates range from 16 to 640 kbps. Each channel can be sub-multiplexed to form multiple, lower rate channels. ARQ - (A)utomatic (R)epeat Re(Q)uest - a general term which describes detection and retransmission of defective blocks of data. When appended to a CONNECT string (eg. CONNECT 28800/ARQ) it indicates that the modems have negotiated some manner of error control for the link. ASCII - (A)merican (S)tandard (C)ode for (I)nformation (I)nterchange. A standard for defining codes for information exchange between equipment produced by different manufacturers. ASYNCHRONOUS - Describes data transmission technique in which the length of time between transmitted characters may vary. Because the time lapses between transmitted characters may vary, a receiving modem must be signaled as to when the data bits of a character begin and when they end. The addition of Start and Stop bits serves this purpose. ATM - An international ISDN high-speed, high-volume, packet-switching transmission protocol standard. ATM uses short, uniform, 53-byte cells to divide data into efficient, manageable packets for ultrafast switching through a high-performance communications network. The 53-byte cells contain 5-byte destination address headers and 48 data bytes. ATM is the first packet-switched technology designed from the ground up to support integrated voice, video, and data communication applications. It is well-suited to high-speed WAN transmission bursts. ATM currently accommodates transmission speeds from 64 Kbps to 622 Mbps. ATM may support gigabit speeds in the future. BANDWIDTH - The frequency range available for use by modems on an ordinary two-wire dial-up telephone line. This corresponds to the frequency range required to reproduce the human voice, or approximately 3500Hz (200-3700hZ). BAUD - Perhaps the most mis-used term in all of the discussions posted in this forum. It actually refers to the unit of measure for the number of discrete changes of state which occur in a communication channel per second (ie. the number of times per second that carrier frequencies are modulated). It is an old term from the days of Frequency Shift Keyed modems. The name honors Jean Maurice Emile Baudot, who invented a bit encoding scheme for characters (it is/was not the same as that presently used for encoding ASCII characters however). Relative to FSK modems, the use of Baud referred to the rate that you could shift from one FSK Tone to another. The tones directly represented the ones and zeros of data being transmitted. In the early days they were generally referred to as the Mark Frequency and the Space Frequency. Accordingly, with this direct correlation of tones to 1s and 0s, the Baud Rate was the same as the Bit Rate. [Note: The FSK transmission schemes referenced above are to bi-frequency implementations such as V.21 and the Bell 103 protocol. Multi-frequency FSK schemes also exist, but they have not been widely implemented over the PSTN]. As more complex ways of transmission were devised it was natural to try to extrapolate this concise definition to define their operation. An early extrapolation was to Phase Shift Keyed (PSK) modems such as the V.26 Series of modems. This was unfortunate, but it did actually occur. The extrapolation went like this: The PSK modem generated a signal with 4 possible phase states and thus 4 possible phase changes. The states were 0, 90, 180 and 270 degrees of the carrier. The possible changes were the same. The data was taken two bits at a time and thus could be as: 00, 01, 10, and 11. Accordingly, the 4 possible phase changes could be directly related to these (4) bit sequences. Now, in this example, the changing of the phases was in line with every other bit, and so at half the bit rate. It was therefore said to have a Baud Rate of half the Bit Rate. So for 1200 bits per second data, the Baud Rate was 600. This extrapolation was actually used in ITU-T Recommendation V.26. Given this fact, it is hard to fault anyone for following it. That is basically the end of the extrapolation, or at least it should have been! It was finally recognized as being inappropriate and is no longer used. If you did a search of Recommendation V.32bis or V.34 you would find that the word Baud is not used in any context. It is simply not found in the recommendations at all. Why then are so many people saying things like the baud rate of V.32bis is 2400? Simply, it is because magazine articles and so-called experts continue to use this poor and improper extrapolation. It is also why so many people try to explain it in different ways and always seem to be in conflict with each other. Frankly, there is NO correct explanation or description. BIT - Acronym for (Bi)nary Digi(t) (ie. 0 or 1). As used in the context of this forum the bit is a basic unit of data. BPS - (B)its (P)er (S)econd - the unit of measure which refers to the data transfer rate between communications devices. The unit by which raw modem throughput is rated. BYTE - Typically a group of 8 binary digits, but can vary from 6 to nine bits depending on the platform. It is a basic unit of memory used to store data in a computer. Additionally, it is the basic element size used when expressing ASCII characters such as you see typed here. [See OCTET] CAS - IBM and DCA standard for computer-fax modem interface. CCITT - Comite Consultatif International Telegraphique et Telephonique (French for The International Telegraph and Telephone Consultative Committee). Now known as ITU-T (International Telecommunications Union- Telecommunication Standards Sector). CLASS - "Classes" refer to the standards defined by technical subcommittee TR-29.2 of the Telecommunications Industry Association (TIA) in the USA. A "Class" (or, formally, Service Class) is a set of capabilities of a fax MODEM (not a fax machine) which is controlled by an extension of the Hayes AT Command Set. Class 1 defines only a few commands (about 10), and provides the minimal set of hardware features in the modem necessary to support fax transmission and reception. Class 2 defines a much larger set of commands (mostly parameters), and requires the modem to implement the ITU-T T.30 fax protocols in the modem firmware. Because the "Class" of a device refers only to the way that fax software talks to the modem and not to how the device works across the phone line with other fax devices, the Class has no bearing on interoperability (assuming, of course, the modem firmware and fax software are correctly implemented!). Class 1 and Class 2 modems and other Group 3 fax devices can communicate with each other across the phone line, in any combination. Class1 - Electronic Industries Association/Telecommunications Industry Association standard for minimal computer-fax modem interface. EIA-578 Class2.0 - EIA/TIA standard for extended computer-fax modem interface. EIA-592 specifies Class 2.0 "Class 2" is a non-standard based on an obsolete draft. CO - Central Office, the telephone company's central switching station for a given area. CPS - (C)haracters (P)er (S)econd - unit of measure for the conjugate data transfer rate, in bytes, between modems. From a user's perspective, this is the bottom line measure of a modem's throughput performance. CRC - (C)yclic (R)edundancy (C)hecking {or Checksum} - an error-detection technique consisting of a cyclic algorithm performed on each block or frame of data by both sending and receiving modems or transfer protocols. CTS - (C)lear (T)o (S)end - flow control parameter which indicates that a device is ready to receive data. DCE - (D)ata (C)ommunication {or Circuit-Terminating} (E)quipment - applies to the device that establishes and controls the data link via the telephone network (eg. a modem). When referring to data flow rates, it is the rate of raw data flow between two modems. DS-0 - The base unit of digital transmission capacity. 1 communication channel = 1 simultaneous voice grade equivalent with a communication capacity of 64 thousand bits per second (64Kbps) DS-1 (T1) - The equivalent of 24 multiplexed voice grade channels (DS-0s). 1.544 million bits per second (1.5Mbps) DS-1C - The equivanlent of 2 multiplexed T1 channels. 3.15Mbps DS-2 (T2) - The equivalent of 4 multiplexed T1 channels. 6.312 million bits per second (6.3Mbps) DS-3 (T3) - The equivalent of 28 multiplexed T1 channels. 44.736 million bits per second (45Mbps) DS-4 (T4) - The equivalent of 6 multiplexed T3 channels. 274.176 million bits per second (274Mbps) DSP - (D)igital (S)ignal (P)rocessor - a semiconductor optimized for handling auio or video signals. DSVD - (D)igital (S)imultaneous (V)oice and (D)ata DSZ - a shareware X,Y, and Zmodem protocol driver marketed by Omen Technology that is most noted for its proprietary extensions/improvements to the base Zmodem protocol. DTE - (D)ata (T)erminal {or Terminating} (E)quipment - The device that generates or is the final destination of data (eg. a computer). When referring to data flow rates, it references to the rate of raw data flow between a computer and modem. DUPLEX - Indicates a communications channel that is capable of carrying signals in both directions. FULL-DUPLEX - Signal flow in both directions at the same time. HALF-DUPLEX - Signal flow in both directions, but in only one direction at a time. SYMMETRICAL/ASYMMETRICAL - Describes whether data flow in a communications channel is balanced or unbalanced (ie. data flow rate is the same in both channels or different). Eg. The USR 16.8K HST protocol is full-duplex asymmetrical, it employs one 16800bps channel and a second 450bps channel. ITU-T V.32bis is full-duplex symmetrical, both channels operate at 14400bps. ENCODING - The process of impressing data onto a carrier. By varying the frequency, amplitude, and phase of the data carrier, it is possible to generate signals which are equivalent to one or more data bits per change of state. Devices which operate above 300bps employ modulation technology which encodes more than one bit per transition. 1200 and 2400bps modems operate at 600 symbols/sec using data encoding techniques that yield 2 and 4 bits per symbol element respectively. Similarly, 9600 and 14400bps modems operate at 2400 symbols/sec using techniques which yield 4 and 6 bits per symbol element. ERROR-CORRECTING MODEM - describes a modem which incorporates data integrity checking protocols in its hardware (eg. MNP4 or V.42 capable modems). When two such modems connect, they transmit data synchronously, obviating the necessity of framing start and stop bits for transmitted data; such modems are thereby able to achieve a 25 per cent increase in throughput relative to non-error-correcting modems. ESCAPE SEQUENCE - A command sent to a modem that will place it in command mode. EXPRESS-96 - A proprietary high-speed modulation protocol developed by Hayes. FLOW CONTROL - A mechanism for compensating for differences in the flow of data input to and output from a a modem. FOSSIL - (F)ido-(O)pus-(S)eadog-(S)tandard-(I)nterface-(L)ayer. A specification detailing the interface between a communications application and a PC's serial communications hardware. Originally conceived to allow programmers to implement common low-level serial I/O functions for their applications on platforms that were not 100% compatible. FSK - [F]requency [S]hift [K]eying. FSK describes the modulation of a carrier (or two carriers) by using a different frequency for a 1 or 0. The resultant modulated signal may be regarded as the sum of two amplitude modulated signals of different carrier frequency. GROUP - the standards that govern the way fax devices communicate with each other across the phone line. Group 3 is defined in ITU-T Recommendations T.4 and T.30, and is the set of capabilities implemented in the vast majority of present fax devices that operate on analog telephone lines (although some recent additions will also permit Group 3 protocols to be used over digital circuits such as ISDN). GSTN - The (G)eneral (S)witched (T)elephone (N)etwork, also referred to as the (P)ublic (S)witched (T)elephone (N)etwork. The PSTN is, by definition, the analog telephone network that provides voice and data access around the world. Digital signals can also be sent after being modulated and sent as an analog signal. When received, the analog signals are then demodulated back into digital signals. This modulation/demodulation by a modem is necessary, as dial-up PSTN lines are not as suitable for digital communications as for voice communications. In actuality, this analog telephone network is now mostly digital, except for the lines from the end offices to the telephone or modem. However, since the connections at both ends are analog, the PSTN can be considered to be essentially analog in nature. "HAYES COMPATIBLE" - A term that implies that a modem implements the [AT]tention command set first utilized on the Hayes Smartmodem 1200. Standardized as EIA602, but varies between manufacturers. Basic "AT" Commands: ATA - force answer mode ATB - select Bell or CCITT modes (all but obsolete now) B or B0 = CCITT B1 = Bell ATD - dial - see your manual for details as this is a flexible and powerful command with lots of neat options. ATE - echo on/off - echo is the copying of a command from the terminal or computer back to it E1 = on E0 = off ATH - hook status, ie. line state H1 = off hook H0 = on-hook ATI - product code or identity code, some manufacturers put in options to provide more or less information about the modem being interrogated, for example: I or I0 = ID and version number I1 = checksum of EPROM I2 = OK or ERROR on validity of checksum ATL - speaker volume L0 = low volume L1 = medium volume L2 = high volume ATM - speaker function M or M0 = speaker off M1 = speaker on until carrier detected (normal) M2 = speaker on while modem on line ATO - originate - force originate mode or resume data state when on line. ATQ - result code output Q or Q0 - normal result codes sent to terminal Q1 - result codes not returned to terminal ATS - set or read S register - see below ATV - result code format output V or V0 - single digit result codes generally most suitable for a computer to interpret V1 - "English" result codes suitable for human interpretation ATX - enable result code formats and tone detection such as busy and dial tone X0 - most basic, just indicate CONNECT X1 - full message indicating line speed, eg. CONNECT 9600 ATZ - reset modem to startup condition Z or Z0 - restore to conditions set in &W0 Z1 - restore to conditions set in &W1 AT&C - DCD/RLSD mode &C or &C0 - DCD always indicated on to terminal &C1 - DCD follows modem carrier AT&D - function of DTR line see your modem manual AT&F - set up factory configuration see your modem manual AT&W - store present configuration in modem's non-volatile memory. see your modem manual and the ATZ command above. These represent only a fraction of the commands available in any one modem, but beyond this, implementations of the AT command set begin to diverge widely and wildly. S-register When implementors of modems are too lazy to conjure up a new AT command for a new function, the function is instead left in something called an S-register. These vary even more widely between manufacturers than do the AT commands, so you are best off to remain away from these if and when you possible can. Good manufacturers will have most or all of the functions in any S-register replicated in an AT command, with the exception of the first 13 "classical" S-registers: S0 = number of rings before modem is permitted to grab the line (0 = no answer, ie. AutoAnswer off) S1 = ring count - read only, cannot be set S2 = escape code character - normally set as "+" to use +++ S3 = carriage return, or RETURN or ENTER, character S4 = line feed character S5 = backspace character S6 = wait after going off hook, before dialling S7 = length of maximum wait for carrier after dial S8 = pause for "," in dial string - see details in your modem's ATD command S9 = carrier detect response time S10 = lost carrier to hangup delay S11 = tone duration during tone dialling S12 = escape code guard time HSP - (H)ost (S)ignal (P)rocessor - a modem that depends of the CPU of the host system for part or most of the data/signal processing. HST - (H)igh (S)peed (T)echnolgy - a family of proprietary high-speed modulation and error-correction protocols developed by US Robotics. IRQ - (I)nterrupt (R)e(Q)uest Line - a hard-wired path to a CPU which requests on a prioritized basis that the processor interrupt a task in progress. On DOS systems, Comm Ports 2 and 4 are assigned to IRQ3, and Comm Ports 1 and 3 are assigned to IRQ4. By virtue of Comm2 and 4 having a lower (thus higher priority) IRQ, it is preferable to have a high-speed device such a a modem attached to it when running multi-tasking platforms which run on top of DOS, or when using multiple serial devices (eg. mouse and modem). ISDN - [I]ntegrated [S]ervices [D]igital [N]etwork is a set of standards for transmission of simultaneous voice, data and video information over fewer channels than would otherwise be needed, through the use of out-of-band signalling. The most common ISDN system provides one data and two voice circuits over a traditional copper wire pair, but can represent as many as 30 channels. Broadband ISDN extends the ISDN capabilities to services in the Gigabit range. BRI- A Basic Rate Interface is two 64K bearer ("B") channels and a single delta ("D") channel. The B channels are used for voice or data, and the D channel is used for signaling and/or X.25 packet networking. This is the variety most likely to be found in residential service. PRI - Primary Rate Interface. Inside North America and Japan, this consists of 24 channels, usually divided into 23 B channels and 1 D channel, and runs over the same physical interface as T1. Outside of these areas the PRI has 31 user channels, usually divided into 30 B channels and 1 D channel and is based on the E1 interface. It is typically used for connections such as one between a PBX (private branch exchange, a telephone exchange operated by the customer of a telephone company) and a CO (central office, of the telephone company) or IXC (inter exchange carrier, a long distance telephone company). ISP - (I)nternet (S)ervice (P)rovider, an organization that provides access to the internet. ITU-T - Formally the International Telecommunications Union - Technical Standardization Sector. it is a consulting arm of the United Nations chartered with the setting of international standards for telecommunications services and equipment. Its members are the national authorities in each country responsible for regulating and providing telecommunication services. It should be noted that though the ITU is chartered with technical tasks, it is a political organization, and therefore subject to all of the trappings thereof. KERMIT - Kermit is a protocol designed for transferring files between micro- computers and mainframe computers. It was developed by Frank DaCruz and Bill Catchings at Columbia University in New York and is widely accepted, especially in the academic world. Kermit was named after the fuzzy, green talking frog of Jim Henson's "The Muppet Show". There are both public domain, and copyrighted Kermit programs that not only include the protocol but are complete programs in themselves offering the communication functions needed for the particular machine on which they are running. LAP-M - (L)ink (A)ccess (P)rocedure for (M)odems - an error control protocol incorporated into ITU-T recommendation V.42. LOCAL LOOP - the copper wires that run between a telephone subsciber's location and the telephone company's switching station. MODEM - The word modem is an abbreviation for MOdulator/DEModulator. Modems are used to modulate, or mathematically speaking to multiply, the data signal onto a carrier signal for transport over a medium where the data signal does not happily go. In our case here, we are talking specifically about modulating RS232 serial data from the serial port of our computer onto an audio carrier for transmission on a telephone line. Historically, modems started out by "multiplying" a slow, simple data stream onto a set of tones. One tone represented a logical binary ON, the other a logical binary OFF. By way of example, we can use the A below middle C at 440Hz, as one tone, and the next higher A, at 880 Hz, as the other tone. If the serial bit stream from our computer looks like: 1 0 0 0 1 1 1 0 1 0 1 1 0 1 0 1 | | | | | | | | | | | | | | | | for example, this modem would send a sequence of: | | | | | | | | | | | | | | | | | | | | 440 880 880 880 440 440 440 880 440 880 440 440 880 440 880 440 using a simple method called frequency shift keying. This sounds like just what it is, a pair of tones flipping back and forth. They are flipping back and forth at the rate of the data being sent. The other end, the demodulator for this simple arrangement, needs only two tone detectors, which are looking for 440 and 880 Hz. The signal is reconstructed from this, and then sent on to the computer attached to it. This basic example is at the heart of modem theory. There are other ways of doing modulation than this simple multiplying. This is also called amplitude modulation, like AM radio, which carrier an audio signal mixed onto a radio carrier frequency. And like radio, there are good reasons why old AM is not necessarily the most effective way to carry a signal. This example above shows that we are encoding our data signal straight on, with no bit encoding. Bit encoding is used for all higher data rates, because if we used simple frequency shift keying, we could only use data rates up to about 1200 bits per second (bps) before Telecom would start complaining that we are using more frequency than we are allowed on a telephone channel. There are important technical reasons for keeping our signal within the width of one telephone channel, ie. between 300 and 3700 Hz. To use a really simple example of bit encoding, we could use 4 tones to encode two bits. We take the following coding, which is only illustrative, to indicate the mechanism: bit1 bit 2 freq 0 0 440 1 0 880 0 1 1320 1 1 1760 and now we re-encode our bit stream: 1 0 0 0 1 1 1 0 1 0 1 1 0 1 0 1 \ / \ / \ / \ / \ / \ / \ / \ / 880 440 1760 880 880 1760 1320 1320 Last time we had to send 16 pieces of information to encode our 16 bits, this time, we only needed to send 8. This information piece is called a symbol element. We are sending, in this example, two bits per symbol element, whereas in the first example, we were sending one bit per symbol element. Extrapolating, with 8 different tones, we could send the same 16 bits of serial information in only 4 symbols. Further, we could send it with only two symbols if we used a 16-level encoding scheme. This sounds wonderful, but there are tradeoffs. For this simple example, using only frequency shift keying, we cannot send data any faster than a few hundred bits per second, otherwise the tone multiplication overlaps the next tone so much we could not decode it at the other end. In order to get away from that, these discrete levels are sent in real modems separated in both frequency and a second dimension called phase. This is getting analogous to FM radio. In radio you can send a signal in both AM and FM on the same carrier, or you can even send two separate radio signals on the same carrier, one modulated AM and the other FM. So too, we can send signals modulated in two fashions, and this lets us get more levels onto the carrier, ie. more bits per symbol. The combination of a different amplitude and phase for each symbol gives us a modulation scheme called Quadrature Amplitude Modulation. DESIGN CONSIDERATIONS On a _very_ basic level, a modem consists of three basic parts; the interface to the telephone line (DAA), a signal processing section (data pump), and a command processing section (controller). The parts can be and indeed are put together in a variety of configurations that can dramatically affect the capability and performance of a given device. This discussion shall be limited to variations in data pump and controller implementations, the DAA design can certainly play a significant role in performance characteristics. The data pump section of a modem is comprised of a digital signal processor and the programming code in which the low-level details of the modulation protocols supported by the device are implemented. DSP code is typically stored in some manner of ROM, but may be hard-coded into an mask programmed integrated DSP chipset [modems which utilize Rockwell chipsets fall into this category (eg. Boca, Cardinal, Zoom, Microcom)], stored in a conventional style ROM memory (eg. USR Sportster [excluding the DSVD model], Motorola Modemsurfr), or stored in field re- programmable (Flash) type ROM memory (eg. USR Courier). In other designs DSP code is stored in driver files on the user's system (eg. USR WinModem, IBM MWave). CAVEATS: In general, operational characteristics relative to basic modulation functions are unalterable when "static" ROM is employed (ie. bug fixes, changes in protocol implementation, or support for new operational modes, cannot be accomplished without physically changing the data pump). The USR WinModem is a special case of the configuration where DSP code is loaded in the form a a driver from the user's system in that it is platform specific - it will only function under Windows incarnations where virtual device drivers are supported (ie. Windows 3.X and Windows 95), IT CANNOT BE USED UNDER DOS, OS/2, WINDOWS NT, OR ANY FLAVOR OF *NIX. The controller section is typically composed of a general purpose CPU and ROM where code governing the command interface, higher-level protocols (eg. error correction and data compression), fascimile functions, and ring pattern recognition, etc, are implemented. As is the case with the DSP section, the type of ROM used varies. The typical design employs fixed ROM, but many vendors have begun to use flash memory in the high-end models. The controller section of the modem is typically what is referred to when a particular model advertises that it employs Flash ROM. MNP - (M)icrocom (N)etworking (P)rotocol - a family of proprietary error correction and data compression protocols developed by Microcom. MNP levels 1-4 are error correction protocols, and MNP level 5 is a complementary data compression protocol which functions under MNP4 error control. NOTE: MNP Levels 1-4 have been placed in the public domain by Microcom. MNP1 Asynchronous, half duplex transfer. MNP2 Error correction, asynchronous, full duplex. MNP3 Error correction, synchronous. Not a big win over MNP2 about 20%. MNP4 Error correction, better throughput than MNP2-3. a modification which rides on top of MNP2 or 3 to improve throughput. MNP5 Simple data compression, about 2:1. MNP6 Statistical duplexing and Universal Link Negotiation. With V.29, modems can emulate full duplex operation. Also supports fall-forward operation between two MNP modems. MNP7 Data compression, about 3:1. MNP8 MNP7 for pseudo-duplex modems. MNP9 Data compression, about 3:1. Includes V.32 technology. (?) MNP10 Dynamic fall-back and fall-forward adjusts modulation speed with link quality. Intended for use for cellular, but doesn't work too well for cellular transmissions! NYQUIST THEOREM - a fundamental dictum of data communications that governs channel capacity. In simple terms it states that frequencies can only be accurately reproduced at up to half the sampling rate. Stated differently, the maximum theoretical signaling speed of a channel in baud is twice its bandwidth. Relative to the telephone system, it dictates that no frequency above 4kHz can be transmitted over a typical phone line. OCTET - An octet is a string of 8 bits, and not necessarily the same thing as a byte. Communications switches transfer information by the octet. If you are using a packet switch to transfer telex messages, then every 8 characters will occupy 5 octets. If you are transferring a binary file from one PC to another, then every 8 characters will occupy 8 octets. PCM - (P)ulse (C)oded (M)odulation, a method of encoding an audio signal in digital format. PEP - (P)acketized (E)nsemble (P)rotocol - a proprietary multi-carrier high-speed modulation protocol developed by Telebit. POP - (P)oint (O)f (P)rescence, a dial-in point for acessing an ISP. POTS - (P)lain (O)ld (T)elephone (S)ervice - an ordinary voice quality telephone line. PROTOCOL - A protocol is a set of rules governing the communication and the transfer of data between two or more devices. The rules define the handling of certain communication problems, such as framing, error control, sequence control, transparency, line control, and start-up control. The Technical Standardization Sector of the International Telecommunications Union, (ITU-T) renders technical recommendations which are typically adopted as standards by manufacturers of telecommunications devices. The recommendations are referenced with an alphanumeric designation of the form V.### which may also include a modifying suffix such as "bis" or "ter" (meaning second and third respectively). The suffixes signify a complementary modification or extension of an existing like-numbered recommendation (eg. V.32 relates to modulation technology for operation of modems on the GSTN at 9600 and 4800bps DCE rates, while V.32bis modifies and extends the scope of V.32 to include rates of 4800, 7200, 9600, 12000, and 14400bps, plus add logic for enhanced retrain turnaround). Similarly, but somewhat different, V.42 recommends error-control methodology, and V.42bis defines data compression technology which functions under V.42 error-control. In addition to the standards established by ITU-T recommendations, manufacturers offer products which feature proprietary modulation or error control technology which may be technically and/or functionally superior to the methods recommended by ITU-T. RBOC - (R)egional (B)ell (O)perating (C)ompany, one of the "Baby Bell" teleco operating companies created by the government mandated break-up of the monopoly formerly held by AT&T in the United States. RETRAIN - A retrain is where the two modems suspend operations and renegotiate the best possible connection all over again. RPI - (R)ockwell (P)rotocol (I)nterface. RPI is a technology that allows error correction and data compression (ECC) technologies to be performed in the PC host computer, rather than in the modem hardware, as has been done traditionally. Technically speaking, RPI is an asynchronous HDLC (High Level Data Link Control) link that operates between a PC and a modem, allowing data compression and error correction to take place on the host PC. This allows RPI to operate using standard PC COMM ports, or standard serial cards. The V.42bis bit stream presented to the remote modem from an RPI modem looks exactly like that which would come out of a traditional hardware implementation of V.42bis, fully synchronous and full duplex. MNP levels 2,3,4,5 are supported as well as V.42 LAP-M, and V.42bis. To get ECC with RPI, as one would get using a hardware implementation of ECC, the PC comm application needs either a driver or a software package that supports RPI; the modem itself needs firmware that supports RPI. RTS - (R)equest (T)o (S)end - flow control parameter which indicates a device is ready to transmit data. SHANNON/HARTLEY THEOREM - further refines Nyquist Theory by taking into account the signal-to-noise ratio of the communications channel in addition to the bandwidth. It is expressed as follows: Maximum bits Available per second = bandwidth x LOGbase2 ( 1 + Signal-to-noise ratio ) SYMBOL RATE - The proper term for what most mistakenly refer to as baud rate. A "symbol" is a waveform transmitted by the modem, which contains a certain number of encoded bits of data to be moved across the link. In simple terms, the Symbol can be viewed as an analog representation of a digital number. Consider a stream of data bits: 1 0 0 1 1 1 0 1 0 0 Now take them two at a time : 10 01 11 01 00 As can be seen there are 4 possible situations, 00, 01, 10, and 11 which one could call A, B, C, & D respectively. The symbol for 00 would be A and for 01 it would be B, and for 10, C and for 11, D (these symbols could be anything agreed to). Thus if you detected a C at your receiver you would know that the transmitter was actually sending you 10 etc. etc. The actual symbols are not alpha characters, of course. They could be, for example, the signal constellation points in the non-trellis coded telephone line signal. Consider this simple constellation: A + ^ | B+-------+C | v + D The points at O, 90, 180 and 270 could be the four (4) distinct Symbols. They would correspond to the A, B, C, D in the example above. We would have just 4 symbol types to detect. The Symbol would change on every other data bit and thus the Symbol Rate would be half the Data Rate. For 4800 BPS the Symbol Rate would be 2400 Symbols per Second. Now consider 9600 BPS. If we wanted the Symbol Rate to still be 2400, as this sets the required bandwidth needed on the telephone channel to carry the modem signal, we must reduce the 9600 rate to 2400. 9600 ---- = 4 2400 This means we must process 4 bits at a time. Four (4) bits can be in 16 combinations as 0000, 0001, 0010 etc. Thus we must have 16 symbol types or points in the un-coded line signal constellation. For Example: + + + + + + + + + + + + + + + + This should be viewed as an expansion of the first constellation example above where the inner 4 points are "like" the 4 points in the above example but rotated 45 degrees. Each point (symbol) would now represent 4 bits as 0000, 0001, 0010, 0011, 0100 etc, etc. Thus, the Symbol Rate is one fourth the data rate. Now for 12000 BPS and a Symbol Rate of 2400, we see we must process 5 bits at a time, and for 14400 BPS and a Symbol Rate of 2400 be must process 6 bits at a time. This latter example would give us an un-coded constellation of 64 points. The noise levels in the channel determine how many bits are encoded in each symbol; lower noise levels allow a greater number of bits per symbol. The bandwidth of the channel limits how many of these symbols may be sent each second. SYNCHRONOUS - Describes a form of data transmission in which blocks of data are sent at strictly timed intervals. Because timing is uniform, no Start or Stop bits are required. TCM - (T)rellis (C)oded (M)odulation. TCM is an optional error correction method included in the V.32 standard. TCM allows modems to check for transmission errors with a redundancy bit, which results in fewer errors on noisy lines. Modems can tolerate twice the noise in the channel than otherwise, using only QAM. Trellis Encoding works with other error correction methods such as V.42. Unlike other methods, TCM is true error correction, in that for small errors, it does not force a retransmit, but actually fixes them. Instead of using a simple 16-point constellation, for example, you force the modem to a higher-density 32-point constellation. The 32-point constellation offers higher encoding density with its "quintbits" (2^5=32), as opposed to the 16-point constellation with its "quadbit" structure (2^4=16). With a given fixed symbol rate (e.g., 2400), the 16-point constellation can deliver data exchange rates of 9600 bps (2400X4). The more-complicated 32-bit constellation offers an intrinsically higher data rate capacity of 12,000 bps (2400 symbols/sec X 5). It's also more susceptible to channel noise because you have to push the individual decision points closer together, and any minor noise perturbation is more likely to cause the distant receiver to make a decoding error. However, instead of using the higher density of the 32-point constellation for speed purposes, suppose you use its added complexity for noise immunity purposes to derive a performance boost. TCM does just that. Instead of operating at 12,000 bps, V.32 TCM transmission remains at 9600 bps with twice as many constellation points as it needs. The extra constellation bits produce a redundant bit. This fifth bit is used as an embedded "checksum" to produce intelligent transmission. Decision rules are used in both the transmitter and the receiver to produce an orderly transmission that is designed to maximize noise immunity. The redundant bit serves an error-detection function similar to the ninth bit used for parity in 8-bit PC memory systems. The memory bit doesn't prevent errors from occurring; however, it flags them and prevents them from propagating. With TCM, the fifth bit acts to help the remote receiver make a high- probability choice among possible alternatives when channel noise has distorted the incoming signal. It doesn't absolutely guarantee error free communication, but helps reduce the probability of errors. The net result is about 4 decibels (a little more than double) the S/N ratio of a non encoded system. TSB38/37A - A network model description and set of testing procedures which are defined in Technical Standard Bulletins of the Telecommunications Industry Association. The TSB37A test suite is used with modem performance test procedures given in TSB38. It is widely used today for comparisons between modems. It models the network as two independent local loops with a four-wire trunk connection between them. Impairments primarily found in the digital network are specified in proportion to their believed presence in the network. For instance, up to three PCM links are included in the tests. ADPCM is also represented. There are also minimal tests that represent the older analog equipment in the network. Each loop and trunk connection specified is assigned a Likelihood of Occurrence percentage (LOO). By multiplying the scores for the loop combination and the trunk, an overall LOO can be assigned to a given test. A LOO of 4% indicates that the results of that test represent 4% of the expected connections in the actual network. UART - (U)niversal (A)synchronous (R)eceiver (T)ransmitter - a semiconductor which interfaces serial ports to the processor buss. FIFO - (F)irst-(I)n-(F)irst-(O)ut - describes the data handling technique utilized by high-performance buffered UARTs such as the NS16550AFN. V.8 - Procedures for starting sessions of data transmission over the general switched telephone network V.17 - ITU-T recommendation of Facsimile operation at up to 14400bps. V.18 - Operational and inter-working requirements for modems operating in the text telephone mode V.21 - ITU-T recommendation for modem communications at 300bps. NOTE: this recommendation is widely utilized outside of the United States and Canada where the Bell 103 protocol is more prevalent. V.22 - ITU-T recommendation for modem communications at 1200bps. NOTE: This recommendation is compatible with the Bell 212A protocol which is prevalent in the US and Canada for devices which operate at 1200bps. V.22bis - ITU-T recommendation for modem communications at 2400bps. Includes an automatic link negotiation fall-back to 1200bps and compatibility with Bell 212A/V.22 modems. V.25 - ITU-T recommendation which specifies a 2100Hz answer tone which is different from the Bell answer tone used in the US and Canada. V.25bis - ITU-T recommended command language for modems. V.27ter - ITU-T modulation scheme used in Group 3 Facsimile for image transfer at 2400 and 4800 bps. It is also used for 4-wire leased line modems. V.29 - ITU-T modulation scheme used in Group 3 Facsimile for image transfer over dial-up lines at 9600 and 7200 bps. V.32 - ITU-T recommendation for modem communications at 9600 and 4800bps. Incorporates fall-back/fall-forward logic for operation on impaired phone lines. V.32bis - ITU-T recommendation which extends the V.32 connection range to incorporate link rates of 4800, 7200, 9600, 12000, and 14400bps. Incorporates logic that falls back to the next lower speed when line quality deteriorates, and fall back further as necessary. Also incorporates fall forward and rapid rate negotiation logic. V.32terbo - 19200bps, with fall back to 16800bps. Designed by AT&T, and is public domain, so any manufacturer can use this standard and put it into their modems. USR has further extended this to support a proprietary link rate of 21600bps. V.32turbo - A modulation protocol developed by Rockwell which extended V.32 link rates to 12000bps. V.34 - ITU-T recommendation for data signalling rates of up to 33.6kbps for use on the general switched telephone network and on leased point-to-point 2-wire telephone-type circuits. V.42 - ITU-T recommendation for modem communications that defines a two-stage process for detection and negotiation of LAP-M error control. V.42 also incorporates support for MNP levels 1-4. V.42bis - a complementary extension of V.42 which defines a specific data compression scheme for use in conjunction with error control. [BTLZ - (British Telecom Lempel-Ziv) the compression technology used in V.42bis]. V.90 - ITU-T recommendation for asymmetric data signalling rates of up to 56Kbps in the direction of a digitally connected server to a capable client, and up to 33.6Kbps in the direction of the client to the server. The technology is based on eliminating restrictions imposed by the conversion of analog signals to digital form in the downstream data path (server -> client). Data flow in the server to client direction does not occur in the form of a modulated carrier, it is instead sent as binary numbers representative of 256 possible voltage levels. The reason for the asymmetrical send/receive rates is because in the direction from the client to the server it is not possible to use a digital coding scheme and make it work as well as v.34 does, thus V.34 is used instead. It isn't possible because the telco's line card has a codec that is a much better digital level changer for the transmit direction than it is for the receive direction. The codec used in the customer's modem is, in that respect, somewhat more sophisticated and was designed to work as a fairly good level changer in the receive direction (which the telco's codec was not designed to do). Note: Achievable bit rates are limited to less than 56kbps in the United States by FCC regulations that limit power input to the network. V.110 - Support of data terminal equipments with V-Series type interfaces by an integrated services digital network V.120 - Support by an ISDN of data terminal equipment with V-Series type interfaces with provision for statistical multiplexing V.FC - V."Fast Class" is the name given to a proprietary modem technology jointly developed by Rockwell and Hayes that is based on the basic features of the proposed V.34 recommendation during the March-April 1993 time frame. While under development by ITU-T, V.34 was given a number of "working" names, the most common of which was "V.FAST". V.FC is not an ITU-T recommendation, despite the "V." prefix. V.FC is incompatible with V.34, but many modem vendors may offer products which support both protocols. + V.PCM - the "working" name of the V.90 protocol while it was under + development by ITU-T SG16. V.Mach - A proposed 43.2Kbps duplex modulation scheme, designed to operate over POTS. X.25 - An ITU-T narrow-band (under 56Kbps) packet switching standard. A forerunner to frame relay and ATM. XMODEM - Xmodem is a file transfer protocol. It was the first file transfer protocol to come into widespread use in the microcomputer world. It was developed by Ward Christensen in the mid-1970's to transfer files between machines running the CP/M operating system. Until the late 1980's, because of its simplicity and public domain status, Xmodem remained the most widely used microcomputer file transfer protocol. The file to be transmitted is divided into 128-byte blocks. Each block is sent in sequence, together with a special starting character, an identifying number, and a checksum. The checksum is a number created by adding all of the bytes in the block together. 1K-Xmodem is an extension to Xmodem which increases the block size from 128 to 1,024 bytes, thereby increasing transmission speeds. YMODEM - As a file transfer protocol, the Ymodem protocol was first released as part of Chuck Forsberg's program YAM ("Yet Another Modem"). Ymodem is actually an extension to Xmodem, to overcome some of the limitations of Xmodem. Ymodem allows information pertaining to the transmitted file to be sent along with the data, such as filename and length. Ymodem also increases the size of the Xmodem block from 128 to 1,024 bytes and adds the capability to transmit "batches" of files. In fact, Ymodem is sometimes referred to as Xmodem-1K, and vice versa. Ymodem-G is a streaming protocol built around the philosophy that no news is good news. It sends the entire file before waiting for an acknowledgment. If the receiving end detects an error in mid-stream, it aborts the transfer. YmodemG is not an error correcting protocol. ZMODEM - As a file transfer protocol, the Zmodem protocol was commissioned by Telenet and placed in the public domain. Like Ymodem, it was also designed by Chuck Forsberg and was developed as an extension to Xmodem, to overcome some of the limitations of Xmodem. Zmodem implements many of the features of the Kermit protocol, as well as the capability to "step down" to the Xmodem or Ymodem protocols on demand. Among the key features of Zmodem are a 32-bit CRC offering a degree of error detection 100,000 times greater than Xmodem CRC, a server facility, batch transfers, and fast error recovery. Zmodem was also specifically engineered to avoid sending certain sequences, such as ESCape-carriage return-ESCape, that the Telenet network uses to control the connection. DATA TRANSFER: Microsoft/IBM/Digital Research-DOS is a single threaded, non- re-entrant, non-preemptive, interrupt driven system. Relative to serial communications, when a byte of data is accumulated in the UART, it signals the CPU via an IRQ to process the byte. IRQs are hierarchical in nature With the most essential system functions being assigned the highest priority IRQs. DOS does not place a particularly high priority on the serial port IRQs, and data transfer errors can occur with high data flow rates, or when interrupt servicing is retarded. The transmission of each byte (or character) requires that 10 actual bits be moved; a start bit, the eight data bits, and a stop bit. The theoretical maximum throughput in CPS for a given DCE is thus derived by the formula DCE/10=CPS. Error correction and data compression complicate this somewhat. Error-correcting modems do not transmit the framing bits, and are thus able to deliver 25% more data throughput versus modems which do not implement error correction. For an error-correcting link the equation becomes {DCE/10} + {DCE/10}x.25=CPS (note that the numbers derived by these equations represent maximums, and that insertion of protocol control information into the data stream will reduce actual throughput ). Data compression techniques can yield additional data throughput advantages over non-error-correcting links, by compressing data before the modem transmits it (some transfer protocols feature this ability as well). Error-correction coupled with data compression can theoretically yield data throughputs which are many multiples of the DCE rate. It should be noted that this is accomplished by reducing the amount of data that the modem has to transmit, via compression, not by increasing the DCE rate. The most important question associated with a communication channel is the maximum rate at which it can transfer information. Information can only be transferred by a signal if the signal is permitted to change. Analogue signals passing through physical channels may not change arbitrarily fast. The rate at which a signal may change is determined by the bandwidth. In fact it is governed by the same Nyquist-Shannon law as governs sampling; a signal of bandwidth B may change at a maximum rate of 2B. If each change is used to signify a bit, the maximum information rate is 2B. The Nyquist-Shannon theorem makes no observation concerning the magnitude of the change. If changes of differing magnitude are each associated with a separate bit, the information rate may be increased. Thus, if each time the signal changes it can take one of N levels, the information rate is increased. As N tends to infinity, so does the information rate. Is there a limit on the number of levels? The limit is set by the presence of noise. If we continue to subdivide the magnitude of the changes into ever decreasing intervals, we reach a point where we cannot distinguish the individual levels because of the presence of noise. Noise therefore places a limit on the maximum rate at which we can transfer information. Obviously, what really matters is the signal-to-noise ratio (SNR). This is defined by the ratio of signal power to noise power and is often expressed in decibels. There is a theoretical maximum to the rate at which information passes error free over the channel. This maximum is called the channel capacity C. The famous Hartley-Shannon Law states that the channel capacity C is given by: C = bandwidth x LOGbase2 ( 1 + SNR) The theorem makes no statement as to how the channel capacity is achieved. In fact, channels only approach this limit. The task of providing high channel efficiency is the goal of coding techniques. The failure to meet perfect performance is measured by the bit-error-rate. THE CONNECTION PROCESS: Communications between computers using modems is a negotiated process. Three data transfer links are established, the DTE at the host, the DCE between the modems, and the DTE at the remote system. DTE parameters are locally established under the control of communications terminal software as limited by the capabilities of the modems. DCE parameter negotiation is somewhat more complex. To effect a link, several precepts must be mutually agreed to by the modems. Information regarding modulation and error-control protocol support is exchanged between the modems, and a connection established ONLY if there is a mutually supported modulation protocol. If the modems do not incorporate a common error control protocol, the link will be established without the benefit of error control. The connect speed will be the highest mutually supported by the modems under the common modulation protocol with the line conditions as they exist at the time of the link negotiation process. ANSWERS TO FREQUENTLY ASKED QUESTIONS: Question: I just replaced my trusty Generic Xpress V.32bis modem with a V.34 model, but it doesn't ever connect at 33.6Kbps. What's wrong? Answer: It is not only perfectly normal, but even typical in a V.34 connection to see a less than 33.6kbps connection. V.34 is not a fixed-speed standard, and makes/changes its connections based on phone line quality. Very few people can get consistent 33.6kbps connections. Speeds of 33.6kbps require pristine phone line quality along the entire length of the connection. V.34 modems are capable of pushing the limits of analog phone lines, commonly offering connection speeds of 21.6k, 24k, 26.4K, 28.8K, and even 31.2kbps. The bandwidth (or "bandpass") of a voice-grade phone line is about 300Hz to 3,800Hz . Because the mathematics of encoding 33.6kbps pushes the phone line to near its theoretical limits, V.34 was designed to accommodate a variety of phone line conditions. V.34 is smart enough to do what is called a "channel probe", which is a frequency response and signal-to-noise ratio test of frequencies at various points across the bandpass. During the modem handshake, the modems send a series of tones to each other, at known signal levels and specific frequencies. The modem calculates the level of the received signal at each frequency, and therefore can determine the maximum bandwidth available for use. So, just how good does a line have to be?! In reality, it takes line clarity at about -44dB or better (about the sound level of a clearly whispered conversation across a medium size room) at the top of the phone line's "bandpass" to obtain and maintain a 28.8kbps connection. At about -46dB and below, modem receivers tend to "go deaf". The typical long distance connection can be much worse than this at that frequency; it is not unusual to see -55dB to -70dB (closer to the background hiss level of a factory-fresh medium-grade audio tape). Standard transmit levels for domestic (US/Canada) modems are approximately -10 dB, although V.34 negotiates these levels during the initial connection attempt. Receiving levels can vary widely, depending on the conditions on your local phone line, the line at the remote modem, and any long-distance or inter-office carrier facilities. Typical receiving levels range from -40 dB at the low end, to -15 dB at the high end, with figures in the -20dB to -35dB range being most common. Extreme values in either direction probably indicate a problem in the connection from your modem to your local phone company, which in some cases the phone company may be able to adjust. However, be aware that Ma Bell and the long distance carriers are not required by law, statute, or tariff to "fix" this "problem" on unconditioned voice grade lines, because it is not really a "problem"! Why does it get bad? Simple line impairment. Variations in line quality are typically the culprit for low connect rates. Line impairments can result in link timeouts (when the error control protocol does not receive a block of data within its expected time frame), link naks (when the error control protocol requests retransmission of data), blers (block errors; errors in received error control protocol or data blocks), and resent data blocks. Everyone occasionally gets "a bad line" and has to hang up and call again to get a better connection. However, if you find that you never or rarely connect at rates above 19.2kbps, you will want to investigate the line quality of your connections. *Try calling a different location. Line quality differs from region to region, and it may be a problem with the lines or modem at the other end of a particular call. *Try connecting with a local call. Sometimes the connections within a long distance call can cause impairments. (If this isolates the problem, you can try switching long distance companies.) *Try plugging the modem to a different phone line or wall jack. *Try eliminating all telephone extensions, phone line surge suppressors, line switches, utility monitoring devices connect to the phone line, and anything else on the line with the modem. *If you know someone else in your area with a high speed modem, ask what type of connections they make. Try making the connection from their location. If you encounter the same low connection rates, the problem may be resulting from impairments along the lines running to the local telephone company or within your home or office. Your telephone company or a private consultant may be able to help. Question: Why is it that the phone company and some of my friends say that it is impossible for me to operate my 14400 baud modem on a normal phone line? Do I really need on of those costly special lines? Answer: This question arises from the improper usage of the term baud in reference to the DCE rate of a modem. It is quite correct that a 9600 -baud- modem will not operate within the bandwidth of a common phone line. It is quite another matter when referring to a 14400 -bps- modem (that operates at 2400 symbols/sec), which certainly will. Question: I just bought a GENERIC XPRESS V.32bis 14400bps modem but can't connect at 14400 with a system that is running a USR HST 14400 modem, shouldn't I be able to connect at 14400? Answer: No, you will only be able to connect at 300, 1200 or 2400bps because Bell 103, Bell 212A, and V.22bis are the only mutually supported protocols the modems have. HST is a proprietary protocol which is only available on some of US Robotics' modems. You should be able to connect at 14400bps with any other modem which is ITU-T V.32bis compliant however. Question: I just bought a Generic Xpress-Lite 2400 modem with V.42bis, and the package it came in says it can achieve 9600bps throughput. but when I call a system I know operates at 9600bps, I only connect at 2400bps, what's going on, shouldn't I connect at 9600? I also notice that my transfer speeds are only slightly higher than they were with my Generic Lite 2400 that didn't have the V.42 stuff (about 285cps using Ymodem-g versus the 238 got with Zmodem-MobyTurbo with the Generic Lite 2400), shouldn't I get the 1100cps or so that other folks do with 9600bps modems? Answer: No, you will only connect at 2400bps because your modem is a 2400bps DCE device. You will get 9600bps DTE data transfer rate between you computer and modem by locking your serial port at 9600bps, but -only- achieve modem to modem effective throughput of 9600bps if the data you are transferring is in non-compressed form. Note that your base link rate remains 2400bps, but that the data compression of V.42bis is capable of effectively quadrupling data throughput. Regarding transfer speeds, you are doing the best you can do with a modem which operates at a 2400bps DCE. The folks with 9600bps modems typically operate with 19200 or 38400bps DTEs and have real 9600bps DCEs. Question: While I was glancing through the manual that came with my Generic Xpress, I noticed it saying something about "Locking" my serial port, enabling CTS/RTS flow control, and changing all of the speed entries in my dialing directory to 38400 or 19200, how do I do this, and why should I? Answer: In order to derive the enhanced throughput benefit offered by hardware error-control, it is necessary to maintain the DTE rate above the DCE rate. This is done so that the modem does not have to wait for data to transmit. Serial port locking is typically an optional function of one's telecommunications software, and the methods to accomplish it are generally detailed in the documentation which accompanies it. As for changing the dialing directory entries, this is done for reason outlined above to correspond to the DTE rate, the DCE rate will be negotiated by the modems upon connection independent of the DTE rate on either end. CTS/RTS flow control is necessary to control the flow of data between the modem and computer. With data being sent to the modem at a rate which is over 2.5 times that at which the modems are exchanging data, a method of slowing down the data flow as necessary is required. Question: When uploading files with my new Generic Xpress, I keep seeing a message flash up on the screen which says FLOW, what is this, and what should I do about it? Answer: The FLOW message is a normal, non-critical indication that CTS/RTS flow control is functioning. It is generated when the data flow rate to the modem begins to strain the capacity of its buffer to store data which is to be transmitted. With data coming to the modem at a rate which is in excess of twice that which it is transmitting, it is a way of it saying WHOA MULE! If it is annoying, it can be eliminated by allowing the DTE rate to adjust downward to the DCE rate (typically referred to as autobaud switching), but it comes at the expense of throughput. Question: I have two computers on the same phone line. Is there anyway I can transfer files between them with the modems? Answer: The answer is yes, you should be able to. You should be able to just simply run a phone extension cord between the two modems, not even hooked up to the actual phones in your house. When going modem-to-modem, no 'MaBell' hookup is required -- at all: 1) Get a standard old telephone cable with a modular plug on each, (like the one you use to hook a telephone to the wall jack). 2) Take one end of this phone cable and plug it into the back of one of the modems. (Into the jack that you would normally use to hook the modem to the wall jack). 3) Take the other end of this phone cable and plug it into the back of the other modem. (Into the jack that you would normally use to hook the modem to the wall jack). ____________ ____________ Like so: |\ \ / /| | \ Back of \ / Back of / | \ \ External \ / External / / \ \__Modem_1__\ /__Modem_2__/ / \ | | | | / \| | | | | |/ ~~~~~~~~~|~~ ~~~~~~~~~|~~ | | +------------------------------+ Standard Modular Telephone Cable Note: You can use the exact same idea with two internal modems or a mix of an internal and external. 4) Now go to the computer hooked up to Modem_1 and load some COMM program. get to the terminal screen. Type: AT and press [Enter] to see if the modem is ready. If it responds with: OK it's ready. 5) Do the exact same thing (Step "4)") over on the other computer, the one hooked up to Modem_2. 6) On either one of the systems type: ATX1D This tells this local modem: ATtention, only give connect responses and ignore the NO DIALTONE, and, Dial (originate the call). 7) On the other other system type: ATA This tells this local modem: ATtention, Answer the call. That's it. Now type something -- on either. They're connected. Comments and/or corrections are welcome either in the echo, Fidonet netmail, or via Internet e-mail. Craig Ford, Moderator Fidonet International COMM Echo aka: cford@ix.netcom.com : craig.ford@2001.conchbbs.comQuestion #23
Hi There! I've done a foolish thing and deleted some very important files in Windows 95. Is there a way that I can retrieve these files back. I know in DOS you used to be able to use a command "undelete" but don't know what to use in Windows.Answer #23
In Windows 95/98 when you delete a file it is not really deleted just put in