16.12   Trouble Shooting Modems

General

From ratman@mailhost.nmt.edu Tue Mar 26 09:22:53 1996

Try the following:

• Load up your comm program (not SLIP or PPP, it takes to long to try things out and makes it difficult to see if it worked or not). Some example programs are Terminal in Windows 3.xx, QModem for DOS, or Telix for DOS. If you have a MAC, find a similar program. Windows '95 also comes with a comm program.
• Make sure the you have software XON/XOFF flow control turned OFF and that CTS/RTS hardware control is turned ON.
• Make sure that you have No Parity, 8 Data Bits, and 1 Stop Bits set up with your comm program.
• Don't connect or dial in. You want to be able to send what you're typing to the modem, not to another computer. To check to see that you're not connected, type AT in the normal area that you type in when connected.

  After a moment, you should get the message OK. If this works you can proceed, otherwise your modem may be defective.

If the above went okay then:

• Phase 1.
  • Type in ATZ and wait for the OK.
  • Type in AT&F2, again wait for the OK message.
  • Next, type in ATDTxxxx, where 'xxxx' is the phone number to call.
  • If you have problems connecting, go on to the next phase.
• Phase 2.

  According to my roommate (who worked in a computer store), you can also try the following. He says it worked with all the 28.8's that the store sold.

  • Type ATZ and wait for OK response.
  • Type AT&F&C1&D2 and wait for OK response.
  • Type ATDTxxxx, where xxxx is the phone number.
  • Go on to the next phase if this doesn't work.

• Phase 3.

  This is a sort of last resort. Most likely, you'll encounter large amount of noise after you try this. This is because this particular string turns every thing off. All error correction, all hardware data compression--it's all turned off. So, if your problem is with either the data compression or the error correction, this will act as an indicator. You will probably have occasion fits of ``noise'' on your screen, garbage that will spontaneously show up or letters that will suddenly show up as being pressed. This is because of little bits of static and noise that are always present on the phone lines. Definitely write back if this step is a solution (as much experimenting and tweaking remains).

  • Type ATZ and wait for OK response.
  • Type \texttt{ATDTxxxx}, where xxxx is the phone number.

If none of this has worked you will want to study your modem manual, especially the sections about the various AT strings. Try several of them, especially the AT&F# series.

It would greatly help us to know what comm program you are using, as well as what you're using it in and on (a MAC, a PC? On DOS, Windows, or Win '95?). Knowing what brand of modem is being used could also help.