The Modem Manual Version 2.0 Copyright 1996 by The West Virginia Rehabilitation Research and Training Center Barron Drive, P.O. Box 1004, Institute, WV 25112-1004 Voice phone (304) 766-2680 TDD (304) 766-2697 Fax (304) 766-2689 Project Enable Bulletin Board (304) 766-2690 Inquiries by E-mail: wvrrtc@rtc2.icdi.wvu.edu World Wide Web: www.icdi.wvu.edu The Project Enable Bulletin Board System can be reached at (304) 766-2690. The Dial-JAN system is available at (800) Dial-JAN. The West Virginia Research and Training Center is supported by a grant from The National Institute on Disability and Rehabilitation Research. The Job Accommodation Network (JAN) is a program of The President's Committee on Employment of People with Disabilities. Copies of this manual are available in alternate formats. ----------------------------------------------------------------- Written by: Dave Whipp and Thomas G. Freeman III Table of Contents * Introduction * What is needed? * Computer * Software * Modem * External modems * Internal modems * Communications Ports * Installing the Software * Installing PKzip * Installing Qmodem * Setting Up Qmodem * Starting Qmodem * Setting the Dialing Directory * Calling an On Line System * Typical Features of On Line Systems * Messages * Files * Database Searches * Other Features * Quitting Qmodem * Appendices * Settings Those Other Communications * Using Higher Numbered Communications Ports * Speeding Up Your Modem * Speeding Up Your File Transfers * High Speed Serial Ports * The V Protocols (V.32, V.42, etc.) Introduction Computer telecommunications is the "art" of using computers and modems to access and exchange information. To a first-time user the details can seem overwhelming and many have given up after a few failed or difficult attempts. This manual is intended to help people with no computer communications experience begin to use their computer and modem. To this end, the information is simplified and only functions necessary for basic access are covered. Computer telecommunications can get as complicated as anyone would like to make it--the purpose of this manual is to keep it simple. The Appendices contain more detailed information on many aspects of on line communication. We will be using DOS computers (IBM and clones) for the purposes of the manual. Apples, Macintoshes, Ataris, etc., each work for telecommunications. Typically the on-line resources you will be using will neither know nor care what type of computer or communications software you use. For the purpose of learning communications software, we will use Qmodem as it is widely available as shareware (try before you buy). Other software may vary in how it is set up and used, but the basic parameters and tasks are the same--only the methods of carrying them out differ. Note: Shareware is not freeware. If you use the software, please register (pay for) it. The income from the software is what allows the authors to keep producing and improving it. What is needed? Computer Nearly any computer works for telecommunications. For the purposes of this tutorial, any IBM PC or compatible with a hard drive should work. If you are using an external modem (described below), the computer will need a serial card (also described below). Software Communications software is what makes the computer and modem work together to communicate with another computer using the telephone system. There are many different communications packages available as both commercial programs and shareware. Some other types of software (e.g., Windows) may include communications capability. We use Qmodem communications software for our examples. This software is widely available and can be "test driven" before it is purchased. Similar "shareware" systems are Telix for DOS and NinjaTerm for Macintosh. Modem The modem is the device that allows the instructions you type on the keyboard to be sent to a remote computer and it prints the information coming from the remote computer on your screen. There are a wide range of modems available and the price has dropped significantly on these. It is recommended to get the fastest (i.e., highest baud rate such as 2400, 9600, etc.) modem you can afford. This will speed up the printing of information on your screen and reduce the amount of time you spend on line when uploading and downloading files. Make sure that your modem is "Hayes compatible" so that it will accept the standard commands from the communications software. You can select other features such as FAX capability based on your needs. There are two basic types of modems: external and internal. An external modem is a separate small box connected to the computer's serial (or communications) port with a cable. An internal modem is a board that is installed inside of the computer case and does not require a serial port. A serial port is a multiple pin connector that is typically located on the back of the computer. Serial ports may be added to most computers by adding a plug-in board. External modems tend to be more expensive than internal ones, but they have a few advantages. Advantages to an external modem are that it is easier to install if you have a communications port available, the "flashing lights" on the front of the box can provide you with useful information, and, when things get totally snafued, you can simply turn the modem off and back on to reset it. Besides the additional expense of an external modem, disadvantages are that it has its own power supply which requires an outlet, the power and modem cables add to the tangled web behind your computer, and it requires some desk space. If your computer does not have a communications port available, you will need to install a serial card. These are inexpensive, but they must be installed inside the computer case. The external modem requires a modem cable to connect it to the communications port. Before purchasing a cable, check to see if the communications port that you want to use has 9 or 25 pins as each type requires a different type of cable. Internal modems are typically less expensive, but they require that you open your computer to install them and you may have to set some switches on the card to select a communications port. A computer can support several communications ports which are generally referred to as "Com1," "Com2," etc. If you have a serial mouse installed on your computer, it will use one serial port and you will need to use a different port. Communications Ports allow your computer to communicate with other devices such as modems. Many IBM "clone" computers have two communications ports installed, typically as Com1 and Com2. If you are installing an internal modem or an additional serial card in such a machine, you will have to set it for a higher numbered port or change one of the existing ports. If both existing ports are not in use, it is often simpler to set one of them for a higher number or disable it altogether than to work out some of the other settings. Your computer or communications port manual should show you how to do this. If you use a communications port numbered higher than two, you will have to take into account the "interrupts" or "IRQ" settings used by the modem card and other devices such as your mouse. If the higher numbered port is necessary, it is suggested to ask your computer dealer or other knowledgeable person for assistance. Appendix B, "Using Higher Numbered Communications Ports" contains an in- depth discussion of this. Installing the Software Now that you have your computer and modem set up, let's install Qmodem and set it up. First, you will need to install the "decompression" software needed for the Qmodem files, then you will install Qmodem. Installing PKzip Qmodem and similar systems are widely available from Bulletin Board Systems (BBSs) and computer users. The files containing the software are generally compressed into a single file to save space and to ensure that you receive all files. A piece of software is needed to uncompress the files. We will use PKunzip (a function of PKzip software) for this. This software is also widely distributed. Pkzip comes as a single file which will uncompress itself when you type the file name to create several files. It is therefore recommended to create a separate file directory to contain these files. To do this: At the DOS prompt, type "MD \PKzip" and press to create the directory. Then type "CD \PKzip" and press to move into the directory. Copy the file containing PKzip into the directory. If the file is named "PKz204g.exe" and the diskette containing it is in your A: drive, type "COPY A:PKz204g.exe" and press . Type "PKZ204G" and press . The program will then create a number of files. Type "DIR" to see a list of the files that have been created. Note that one of these is "Manual.Doc." This contains a manual for PKzip software and can be viewed on the screen or printed. Notice that there are other files which end in ".Doc." These are also text materials that explain features and give information on how to register the software. As you use on line systems, you will likely download software to try on your computer. Much of it will be in compressed files and you may need PKzip to uncompress these. Installing Qmodem The installation of the Qmodem communications software is much like PKzip installation: create a directory, copy in the Qmodem files, then uncompress them. At the DOS prompt type "MD \Qmodem" and to create the directory named "Qmodem." Then type "CD \Qmodem" and press to move into the directory. Qmodem is typically distributed in two or more compressed files. If the files were named "QM45D-1.zip" and "QM45D-2.zip" and on a diskette in your drive A:, you would type "COPY A:QM45D-?.zip" to copy both files at once. (The "?" is a "wild card" that allows any character to be substituted.) Notice that these file names end with ".Zip" indicating that they are compressed using PKzip. Use PKzip to uncompress these by typing "\PKzip\PKunzip *.Zip" and pressing . The files will be listed on the screen as they are uncompressed. Type "Dir" for a directory of the files that have been created. Notice that there are a number of files with names that end in ".Doc" and that there is also a file called "Read.Me." The Read.Me file will give general information about Qmodem, and the .Doc files will provide greater detail. You will find a "Read.Me" file included with many pieces of shareware and it is generally intended to be the file read first. Setting Up Qmodem Before running Qmodem the first time, it is necessary to run an install program to locate the modem and provide a few other pieces of information to the program. Type "Qinstall" to start the installation program. The installation program will attempt to tell if you have a color system, but will ask you to confirm whether you want color by typing "Y" or "N" and pressing . You will then get a screen of instructions on how to continue with setup. Press again to go into the setup mode. Notice that you now have a "Menu Bar" across the top of the screen. You move from option to option using the arrow keys or by typing the first letter of the option. There are many features that can be controlled here but we are only going to set the minimum number necessary to begin using communications. The options you do not set now can be explored later and the settings you make now can be changed. (Appendix A, "Those Other Communications settings," explores more of these.) Move the highlighted area to the word "Modem" in the menu bar, then press to get a "Pull-down" menu. The first feature in this menu "Communications Parameters" will be highlighted. Press again to pull down this menu. You will set several options here. The first option in the list is "Default baud rate." Set this to the fastest speed that your modem can use. (The modem will typically be labelled as a "2400 baud modem," "9600 baud modem," etc.). Press while the baud rate area is highlighted, then use your up and down arrows to highlight the correct speed. Then press to go back to the menu. (See Appendix C, "Speeding Up Your Modem," if you are using a 9600 baud or higher speed modem, or if your modem has MNP or V.42 capabilities.) Unless you know that the computer you will be calling uses different settings than what is shown, leave the others as they are now set, except for the "Serial port" setting which must be set for the port used by your modem. Again move to the "Serial port" label with the up and down arrows, press to get a menu of communications ports and use the arrows to select the correct port. Notice that only communications ports 1 and 2 are listed. (If you are using port 3 or higher, see Appendix B, "Using Higher Numbered Communications Ports.") Now press the key once to go back to a higher level of menu. Use the arrow keys to move the highlight to "Quick Modem Config." Press to get a list of modems and use the arrow keys to highlight the name of your modem, then press . If your modem does not appear in the list use the appropriate "Generic" selection from the list. This will automatically provide the settings for your modem. You will then be asked if the setup commands should be sent to the modem. Answer "Y" and, if you get a message that the commands were successfully sent, your modem settings are correct. Tap a key to remove the message, press once only to return to the top menu bar. Press "E" for Exit, then "S" to save the settings, and you will exit the setup program. Starting Qmodem You may now start the regular communications package by typing "Qmodem." You will most likely not need to use Qinstall for future changes as it can now be run from within Qmodem. Press and "N" together now and notice that you get the setup menu bar across the top of the screen. Press "D" to set the directories that you will use for files that you want to upload to another computer and where you want to store files that you download. With the highlight on the "Upload" line, press to go into the editing mode, then type in the name of the directory to use. If many of the files you want to share with others are text that you have created using your word processor, you might enter the name of the directory where your word processing files are located (e.g., "C:\Documents"). Move the highlight down to the "Download" line and enter the name of a directory where you want to store files you receive from other computers. Now press once to move back to the main menu bar, then type "E" to exit and "S" to save the settings. You can explore other settings as you need them using the same process. Setting the Dialing Directory Qmodem, like most communications software, will automatically dial a phone number if it is entered into the "dialing directory" or phone book. To access the dialing directory, press and "D" at the same time. This will bring up a directory that already has entries for the companies that create and market Qmodem. To enter the number of a system you want to call, use the arrow keys to move to a blank line, then press "R" to revise the entry. This will bring up a form to collect information on the system. To fill in the form, locate the highlight on the proper line. If the information is text such as the name of the system just type it in and press . When entering the phone number, you can use any symbols such as "(" or "-" to make the number easier to read. Remember to put in any numbers that may be needed to get the call through an office switchboard or to call a long distance service. To make the dialing pause, put in one or more commas. You may need to experiment to get the pauses right. The number for the Project Enable BBS is (304) 766-2690. You can use this one for starters if you don't have another system in mind. Unless you know that you need to change the other settings, leave them as they are for now. You can go back and revise your entries later as you learn more about communications and about the system you are calling. (If a system you intend to call uses "7 bit words," or "even parity," see Appendix A, "Those Other Communications Settings." Press F10 to save the entry and go back to the dialing directory. Calling an On Line System You are now ready to make a call. Simply highlight an entry in the dialing directory, and press . If everything is set correctly, you will hear the dial tone, the touch tones, and a high pitched squeal when the remote systems answers. From now on, all you have to do to make this same call is to start Qmodem, Press and "D" together to get the dialing directory, highlight the number to call, and press . Typical Features of On Line Systems While there is tremendous variation in the features of various on line resources, there are several broad areas that tend to be available. Messages Messages and electronic mail (also called email and netmail) are the capacity for exchanging messages with other users. Typically both public (can be read by all users) and private (can be read by only the person to whom it is addressed) messages are available, although there may be limitations on the private messages. Quite often messages are broken into special interest areas (e.g., spinal cord injury or diabetes) called conferences, forums, discussion groups, etc. These special interest areas may be confined to users of that particular system or they may contain messages from other systems around the world. Messages that are shared with other systems are often referred to as "echomail" as a message that is left on one system is "echoed" to all systems that carry that special interest area. Echomail messages cannot be private--netmail must be used for private messages to a person on another system. Some systems allow you to send mail directly to an individual on another system. This electronic mail is often called "netmail." Files Many systems have large libraries of files that you may download to use on your computer. These files may be text (e.g., the Americans with Disabilities Act) or software (e.g., a "sticky keys" program for people who cannot type with both hands). Systems often invite you to upload files to share with others. When downloading or uploading files, you generally tell the system that you are connected to that you want to transfer a file. The commands for this are often "D" for download or "U" for upload. You may then be asked for a filename and a "protocol." Your communications software and the remote system must use the same protocol. If Zmodem is available on both, it is highly recommended, followed by Ymodem, then Xmodem. (See Appendix D, "Speeding Up Your File Transfers" for more information on protocols.) After telling the remote system that you are going to download or upload a file, you must then tell your system to follow through. Qmodem uses for a download and for an upload. Database Searches Many systems have searchable information systems which are sometimes referred to as "doors." These may allow you to search through a law or locate publications from a catalog. The methods of using these vary considerably from system to system, so read the instructions carefully on the systems that you access. Other Features Most systems have extensive help information available. Check the screens and menus for instructions on getting help. Many systems also have a system of "bulletins" that contain information about the system and its features. It is a good idea to look at these when you begin to use a system. Quitting Qmodem After logging off the on line system, you can quit Qmodem by pressing and together. If you have turned the "Doorway mode" on (see Appendix A), this command will not work until Doorway is turned off. Appendices Appendix A Settings Those Other Communications There are many settings involved in computer telecommunications. Here is some information on settings not covered in the main body of this text and some additional information on items that were covered in less detail. Baud Rate: Unless you experience problems connecting to a system, always set the baud rate to the highest rate your modem can support. Nearly all modern modems will connect to the fastest speed available and adjust your com port accordingly. If you have a high speed modem, you can usually set this to 38400 or 57600 (see Appendix C, "Speeding Up Your Modem"). 8-N-1: If you see "8-N-1" or similar numbers in your dialing directory, they usually refer to the following: Data Bits: Always 8 unless Parity is not set to N (None), in which this will be set to 7. Parity: Unless otherwise instructed, set parity to N (None). Some systems require odd or even parity. If after connecting to a system, you get short bursts of funny characters on your screen, this may indicate a parity mismatch. If this happens, try setting the parity to "E" or "O". Stop Bits: Always set to 1. Duplex: Bulletin Board Systems usually operate at Full Duplex. Terminal Emulation: Terminal Emulation determines how your computer translates incoming data to your screen. It allows characters to appear on your screen in different colors and intensities. It typically allows the use of up and down arrows and other cursor movement keys. The most common terminal emulation on Bulletin Board Systems is ANSI. ANSI allows for basic colors, flashing characters and changing intensities. Some communications programs such as Qmodem or Telix also allow for simple tones or music to be sent across the modem, although ANSI Music is rarely utilized on BBSs. When in doubt, always choose ANSI as your terminal emulation when calling a new BBS. A superset of ANSI often used on mainframes or VAX/VMS systems is the VT series: VT52, VT100, VT101, VT200 (depending on the number of keys on your keyboard). These allow a limited use of your function and arrow keys. Because the VT series is a superset of ANSI, it can be used in place of ANSI if ANSI is not an option for you. The VT protocols are not standardized among communications programs; thus, you will find wide differences in the performance of these modes between different programs. A fairly new terminal emulation that is rapidly gaining acceptance is RIP (Remote Imaging Protocol). RIP terminal emulation allows you to move your mouse and click on options in a graphically oriented menuing system (sort of like Microsoft's Windows environment) instead of typing in letters on a keyboard. Doorway Mode: Some communications software has a "Doorway mode" which is usually activated by hitting the and <=> keys together on your keyboard. "Doorway mode" allows every key on your keyboard to be recognized by the other computer. On some bulletin boards such as Project Enable, Doorway mode is useful in situations such as the full screen editor, where you can use your arrow keys, Delete, Insert, PgUp, PgDn, End, and Home keys to help you move around when entering a message. You will need to "turn off" Doorway mode by pressing <=> again before the command keys will work to pass instructions to your communications software. For example will not start a file transfer when Doorway mode is on and will not allow you to exit Qmodem until Doorway is turned off. File Transfer Protocols: A file transfer protocol is the method in which you transfer files between the bulletin board and your machine. "Uploading" means sending a file from your computer to the bulletin board, while "Downloading" means receiving a file from the bulletin board to your machine. Typical protocols are Kermit, Xmodem (Sum), Xmodem CRC, 1K-Xmodem (sometimes erroneously referred to as Ymodem or Old Ymodem), Ymodem Batch (or "True Ymodem"), and Zmodem. See Appendix "X" for more information on File Transfer Protocols. Both the sending and receiving machine must be set to the same transfer protocol for a transfer to be successful. Therefore, you will typically find yourself typing in the protocol and the filename two times: First, you will tell the bulletin board you wish to transfer a file. When all of the necessary information is entered, the system will tell you to "Start Your Transfer". Then you will need to tell your communications program you want to transfer a file and which protocol will be used. Fancy protocols such as Zmodem may automatically communicate with your communications program saving you from performing the second step. (Appendix D, "Speeding Up Your Modem" has more information on this.) Appendix B Using Higher Numbered Communications Ports Communications Ports (also known as serial or COM ports) are connections where you plug modems, mice, and other devices into your computer. Your computer accesses these ports by an "IRQ" (a "hardware interrupt address" or signal which tells the computer that the device using the port is issuing commands). Unfortunately, COM ports on most machines were originally designed to share IRQs. COM ports 1 and 3 typically share IRQ 4, while COM ports 2 and 4 typically share IRQ 3. Thus, when a person tries to install a device such as a mouse or a modem on COM 3 or COM 4, he may find the device acting oddly or not working at all. This is because the device on COM 3 and COM 4 ends up conflicting with the device on COM 1 and COM 2. Modems will always end up conflicting with any other device trying to share its IRQ. There are several ways around this: 1) Don't use COM 3 and COM 1 at the same time and don't use COM 2 and COM 4 at the same time. This is to say, don't use COM 3 with a modem if you are using COM 1 for a mouse unless you turn the mouse off while you are running your communications software. This is the easiest way to avoid problems, but it may not be an option for some. 2) Many com ports and internal modems allow you to switch to a unique IRQ. If your system allows this, try this: See if you can switch a COM port to IRQ 5 or 7. If you are switching your modem, make sure your communications program allows you to switch the IRQs on your com port. Also keep in mind that lower IRQs are serviced faster; thus, if you have a high speed modem, you will want it on the lowest IRQ (IRQ 2, used by COM 2 normally) that you can place it on. (Note: You cannot use IRQ 1 - it is used by your keyboard!) Using COM3 or 4 or a new IRQ with Qmodem If you plan on using COM 3 or COM 4 with Qmodem, or if you have changed the IRQ for your COM port, you will need to tell Qmodem where to find the COM port. You can do this by first selecting Install (Alt-N from Qmodem, or QINSTALL from DOS), selecting "Modem", then selecing "Port Setup". Here you will be able to select both a new IRQ and Base Address for your COM port. Hitting F1 will give you a help screen if you're not sure what Base Address to use. Also notice that Qmodem will attempt to deactivate devices sharing the same IRQ as your modem (such as a mouse) to prevent the devices from conflicting with each other. Hitting F1 will give you more information with this feature as well. Appendix C Speeding Up Your Modem Most modems on the market today, especially high speed modems, are capable of communicating at speeds faster than the connection rate shown on your screen when the remote system answers. This is nearly always the case with 9600 or faster modems, or if your modem has MNP or V.42 data correction. (A number of 2400 baud modems have these features.) A modem advertised as capable of 9600 "bps" (bits per second) will actually with the proper connection transmit/receive data at 12,000 bps or faster. A modem advertised as capable of 14,400 bps can actually transmit/receive data at 18,000 bps or faster. MNP5 and V.42bis data compression can further increase your speed from 30% - 400%. (See Appendix F, "The 'V' Protocols" for more information on data compression standards.) The reason for this is that communications between your computer and the modem can actually run faster than the communications between your modem and the modem on the remote system. Thus, you may find that your communications program is slowing down your modem's performance if it is not properly configured to handle speeds faster than 9600. While this usually won't cause errors, it can cause you to spend more time on-line than need be. There are several things you can do to keep your modem running at top speed. These hints only apply to high speed (9600 or above) modems or modems with MNP5 or V.42bis data compression. 1 -- Check the configuration settings in your communications program. There is usually a place to enter in a default modem speed for your dialing directory. Set it to the fastest speed your modem can handle (check your modem's documentation to see what rates it supports). Often, this can be 19200, 38400, or even 57600 baud. 2 -- -- Check the dialing directory in your communications program. Many communications programs require you to set a speed for each phone number in the dialing directory. You will always want to use the fastest speed your modem can handle. Don't worry about what speed the system you are calling can support; your modem will adjust and automatically pick the fastest speed it can connect with, but only when you have your modem set to call at its fastest speed. 3 -- Check your modem's documentation to find how to "lock your DTE" at the rate you have selected. The "DTE" is the rate between your modem and computer, and should be set to a fast fixed rate of 19200, 38400, or even 57600 if your modem is capable of that speed setting. If the DTE rate is not locked, your modem will slow down to the initial speed at which it connects. Once you have locked the DTE, you can enter in 19200, 38400, etc... as the speed you wish to dial out in your dialing directory. You can usually lock the DTE rate on your modem by entering the following two commands to your modem from your terminal: ATZ AT&B1&W Not all modems will accept the above command sequence, so be sure to check your modem's documentation before using it. Appendix D Speeding Up Your File Transfers When uploading or downloading files from an on line system, you will find the differences between file transfer protocols (the method used to transfer a file) to be more extreme when using a high speed modem. Protocols such as Xmodem and Xmodem CRC, for example, which may give a satisfactory performance at slow connect speeds, may only give you a transfer rate of 5600 bps with a 9600 bps modem. The reason for this is that protocols such as Xmodem, Xmodem CRC, and Ymodem will stop after a certain amount of data is sent and wait for the receiving computer to acknowledge receipt of the data. With slower modems, this pause is insignificant, but with high speed modems it can take up over half of the transfer time involved, making their efficiency rating less than 50%. Newer protocols such as Zmodem and Ymodem-G are more effective because they do not stop to wait for the receiving computer's acknowledgement before continuing. Without these pauses, these protocols can come close to 100% efficiency. Zmodem has sophisticated error checking yet still achieves between 90-100% efficiency. Zmodem also has other features, such as "file recovery". If you are downloading a large file and your connection is disrupted causing you to call back, Zmodem will let you continue downloading where you left off when you start to download the file again, saving you from downloading the entire file. Zmodem is typically the favorite on Project Enable. Ymodem-G sacrifices error checking for speed, making it the fastest protocol available. With no error checking involved, data is sent at full speed with no stops. Error checking is expected to be handled by the modems. If both your modem and the modems you call do not handle error checking, Ymodem-G will not be an option for you. With a high speed modem locked at 38400 or 57600 and using Ymodem-G, you can see transfer of compressed files reach 17000 bps (or 1700 cps - characters per second), while transfer of text files can reach the limit of 38400 or 57600 bps. Appendix E High Speed Serial Ports External modems are usually connected through your computer's serial (or communications) port. The serial ports on many computers cannot handle speeds over 9600 baud properly. The chip at fault is called the UART (Universal Asynchronous Receiver Transmitter), a large rectangular chip that sits on the serial card in your computer. These chips normally have an identification number printed on them that shows what chip is in your card. A number of chips have been used over the years and some of these are more efficient than others. The 8250 and 16540 series UARTS may be unreliable. The newest series, the NS16550AFN UART, has been designed to handle high speed communications and even has a small buffer built into it. If you experience an excessive amount of errors when transferring a file at speeds greater than 9600 bps, you may want to check to see what kind of UART is in your serial port. The program Is16550.com will tell you which series UART you have and recommend a replacement if necessary. The program is available for downloading from Project Enable as Is16550.Zip. When Qmodem is started, it will display the type of UART chip found. The 16550AFN series UART can often be easily replaced on your serial card. The chip can be purchased from many mail order houses for as little as $13. If your old UART is not soldered into your serial card, you can replace it yourself with the new 16550AFN UART if you have a chip puller. If the old chip is soldered in or if your serial port has a non-standard or VLSI UART(smaller square chips), you may need to purchase a new serial card with replaceable UARTS or with a 16550AFN UART chip already installed. Appendix F The "V" Protocols (V.32, V.42, etc.) Specifications for modems, especially the high speed ones, often have a bewildering array of letters and numbers listed as standards and protocols. These can be quite confusing particularly when a modem has many features such as FAX capability. There are two types of standards: ITU-T (formerly CCITT), and proprietary. ITU-T stands for the International Telecommunication Union-Telecommunication sector, an international organization that sets the standards for telegraphic and telephone equipment, such as modems and FAX machines. This ensures that a standard for communications can be established with modems from different manufacturers. Proprietary standards are developed by a single manufacturer and typically are effective only when two of that manufacturer's modems are communicating. Note that the order of the numbers for these standards is not significant (i.e,. higher does not mean better). Modem Data Speeds These are the some of the standards that modems use to send computer data between computers. V.32 ..... The ITU-T standard for modems to send/receive data at 9600 bps. V.32bis .. The ITU-T standard for modems to send/receive data at 14,400 bps. V.34 ..... The ITU-T standard for modems to send/receive data at 28,800 bps. Also known as "V.FAST" during it's development. V.FC ..... This is a proprietary standard not recognized nor endorsed by the ITU-T, for modems to send/receive data at 28,800 bps. Sometimes referred to as "V.FAST CLASS" It was created by Rockwell for modem companies that wanted a faster data rate than V.32bis but couldn't wait until V.34 was officially released. It is based on an earlier implementation of V.34. At the time of this writing, it is not expected that V.34 and V.FC would be compatable with each other, but it is also expected that most V.34 modems will be capable of communicating with V.FC modems at high speed. V.32terbo This is another proprietary standard not recognized nor endorsed by the ITU-T, for data transmission at 19,200 bps. HST ...... A proprietary standard for communication at 9600, 14,400, or 16,800 bps, used by US Robotics on their HST modems. HST has proven to be very popular among amateur BBSs. Modem FAX Speeds FAX transmissions must use different protocols than the ones used for data transmissions. Thus it is possible for a modem to be capable of a 14400 bps FAX rate but only a 9600 bps data rate, or vice versa. Keep this in mind if you are shopping for modems with FAX functions built in. V.29 The ITU-T standard for FAX transmissions at 9600 bps. V.17 The ITU-T standard for FAX transmissions at 14,400 bps. Data Correction Data correction checks for errors in transmissions of computer data and resends the data if an error is found. MNP ..... Protocols established by MicroCom to establish error-free connections between two modems. Levels 1 through 4 are for data correction. V.42 ..... The ITU-T standard for establishing error-free connections between two modems. This includes MNP levels 1 through 4. Data Compression Data Compression "shrinks" data files by substituting codes for commonly used sets of characters. This allows a file to be transmitted much faster. If the files to be transferred are already compressed (e.g. "zipped"), these compression techniques don't work and some can even slow down the transfer. MNP5 ..... MicroCom's protocol for data compression. When already compressed data is sent across modems, MNP5 cannot deactivate itself, so transfer efficiency is slightly reduced when transferring compressed files. Thus, its use is only recommended when you do not intend to transfer compressed files. V.42bis .. The ITU-T approved method for compressing data between modems to speed transfers. Unlike MNP5, V.42bis data compression automatically shuts off when transmitted data is already compressed. ---------- End of Document