TECHNICAL BULLETIN #183 - Rev 1.10 (7/05/96) ============================================================================== TITLE : Connecting to a Low-Speed Modem PRODUCT : Procomm Plus 4.x, 3.x ============================================================================== Sometimes a high-speed modem is unable to connect to an older low-speed modem. Forcing the high-speed modem to behave like the low-speed modem often fixes this problem. To do this, you will need to turn off the modem's built-in error correction and data compression by using either NORMAL mode or DIRECT mode. NORMAL MODE VS. DIRECT MODE These two modes are very similar in that neither uses error correction or data compression between the modems. The difference is in the use of data buffering and flow control. With NORMAL mode, the modem will buffer data and use the flow control specified by Procomm plus. With DIRECT mode, the modem will not buffer data and will ignore flow control. Important! 1. Do not replace your current initialization string with a normal mode or direct mode string; odds are you will not want to use normal (or direct) mode more than occasionally. Instead, create a separate MetaKey entry (described at the end of this document) so that pressing Alt-J will restore your default modem setup (in most versions). 2. Having a Hayes compatible modem does not mean you should use the Hayes settings. "Hayes compatible" refers to the basic command set used by your modem. The commands controlling normal, direct, or reliable mode are not generally part of the basic set. 3. The list below includes a "Generic Rockwell" modem. This is not a brand name, but the name of a very popular chip manufacturer. The majority of modems currently on the market use Rockwell chips. ============================================================================== NORMAL MODE COMMANDS: ------------------------------------------------------------------------------ Modem Brand: Command: ------------------------------------------------------------------------------ AT&T modem: AT\N0%C0^M Best Data modem: AT\N0%C0^M Boca modem: AT\N0%C0^M Everex modem: AT\N0%C0^M Generic Rockwell modem: AT\N0%C0^M Hayes modem: AT&Q6^M Megahertz modem: AT\N0%C0^M Microcom modem: AT\N0%C0^M Multitech modem: AT&E0&E14^M Practical Peripherals modem: AT&Q6S46=0^M Prometheus promodem: AT*E0^M Racal modem: AT*E0*D0^M Supra modem: AT\N0%C0^M Telebit modem: ATS95=0S66=1S51=252S50=254^M USRobotics modem: AT&M0&B0^M Zoom modem: AT\N0%C0^M ============================================================================== DIRECT mode commands: ------------------------------------------------------------------------------ Modem Brand: Command: ------------------------------------------------------------------------------ AT&T modem: AT\N1%C0^M Best Data modem: AT\N1%C0^M Boca modem: AT\N1%C0^M Everex modem: AT\N1%C0^M Generic Rockwell modem: AT\N1%C0^M Hayes modem: AT&Q0^M Megahertz modem: AT\N1%C0^M Microcom modem: AT\N1%C0^M Multitech modem: AT&E0&E14&E3&E10^M Practical Peripherals modem: AT&Q0S46=0^M Prometheus promodem: AT*E0*F0^M Racal modem: AT*E0*D0*F0^M Supra modem: AT\N1%C0^M Telebit modem: ATS95=0S66=0S96=0^M USRobotics modem: AT&M0&H0^M Zoom modem: AT\N1%C0^M ============================================================================== FIXING THE BAUD RATE Some modems may also require that you fix the baud rate of your modem to match that of the low speed modem. In fixing the baud rate, most brands will need the string N0S37=n added before the ^M, where 'n' represents a baud rate. To determine the value of n, use the chart below: ----------------------------- Baud rate needed= n= ----------------------------- 300 3 1200 5 2400 6 4800 7 9600 9 ----------------------------- For example, if you have a Supra modem and the remote requires a baud rate of 2400, you would use the string AT\N0%C0N0S37=6^M. Other brands may use different commands. AT&T modems use the %Bn command, where n is the baud rate (n=300, 1200, 2400, 4800, 9600). To fix an AT&T modem to 9600 baud in direct mode, you would use the string AT\N1%C0%B9600^M. US Robotics modems use the &Nn command. To determine the value of n, use the following chart: ----------------------------- Baud rate needed= n= ----------------------------- 300 1 1200 2 2400 3 4800 4 9600 6 ----------------------------- For example, if you have a US Robotics Sportster modem and the remote modem requires a fixed baud rate of 1200 in normal mode, use the string AT&M0&B0&N2^M. IDENTIFYING YOUR MODEM If you do not know the modem brand, but have a manual, use it to identify the appropriate commands. You should look for the following words or phrases in the index: "Error Correction", "Data Compression", "V.42", "MNP", "Normal", or "Direct." You may also find some reference to disabling error correction and data compression in the specifications section. If you do not have a manual, use the following steps to find a normal mode setting that works for you: 1. Type ATI3 and press . Many modems will respond with manufacturer information which could tell you a brand name and possibly even the model of your modem. You should also try ATI4, ATI5, and so on up to ATI10. One or more of these commands may tell you manufacturer information. 2. Start by typing AT\N0 at the terminal window and press . If the modem responds with OK, the modem is most likely a rockwell modem; you may stop here and use the generic rockwell settings from the list above. 3. If the second step returned an ERROR, type ATI4 and press . If the response includes "USRobotics", use the setting for the USRobotics modem above. 4. If the third step does not indicate a US Robotics modem, try typing AT&Q5 and press . If the result is OK, you probably have a Hayes modem and use the Hayes settings above. If the result is error, and the modem is a 2400 baud or lower modem, set it up as a Hayes compatible 2400 baud modem. 5. If none of the above are correct, try typing ATS131=1 and press . If it returns OK, you probably have a Telebit modem; use the settings from the list above. 6. Failing all of the above, try typing AT$H1 and press . If the modem returns a help screen displaying possible settings, you may have a Multitech modem; use the settings from the list above. Also, some Practical Peripherals modems respond to AT$H with a help screen. ADDING A METAKEY ENTRY In every Procomm plus product from Quarterdeck the metakey editor can be reached by pressing Alt-M from the terminal window. Locate an unused metakey (in each windows version, the ninth metakey is unused by default), and use the text or send text action, followed by the appropriate AT command in the contents section, plus an appropriate label. ============================================================================== To ensure that you have the latest version of this document, compare its revision number to that of the same document on any of our support sites. This technical bulletin may be copied and distributed freely as long as it is distributed in its entirety and it is not distributed for profit. Copyright (c) 1996 Quarterdeck All rights reserved. ==============================================================================