9600 BPS Faxmodem  (250-3030)     Troubleshooting      Faxback Doc. # 5241

When you have problems transmitting data with your modem (garbled data, 
intermittent errors, and so on), check to see that:

* The phone connection is clean and noise-free.
* No one is talking on the telephone line.
* The phone and all extensions are on the hook.
* The operation speed is correct for the modem you are using and the modem .
  with which you are communicating.

If you still cannot transmit data, disconnect your modem to see if the phone 
line is operating correctly. If it is, the trouble is probably in your modem. 
Take it to your local Radio Shack store for further testing and/or repair.

Also, the telephone company can change its lines and/or equipment. If these 
changes affect your modem or its connection, the phone company notifies you 
in writing so that you can take steps to ensure uninterrupted service.

Diagnostics:

Your modem has built-in diagnostic capabilities. Test patterns for the analog 
loopback can be generated by either the modem or the computer. You use the 
test commands (&T) outlined in "Modem Test Commands" to perform these test. 
The modem does not respond to an incoming call while in the diagnostic mode.
For further information on the testing mode, refer to Faxback Doc. # 4877.

Lightning:

Your modem has protection circuits, which meet or exceed FCC requirements, 
to reduce the risk of damage from surges in telephone and power line currents. 
However, lightning striking near or on these lines can damage the modem. A
strong enough power surge can not only damage your modem, but may also
damage your computer because the modem is directly connected to your 
computer's circuits.

Lightning damage is uncommon. However, if this concerns you or if you live 
in an area with frequent and/or severe electrical storms, we suggest that 
you unplug your electronic equipment during the storms. Alternatively,
surge protectors exist for both power lines and modem lines.

If the other modem answer, but doesn't connect....

Your modem normally tries to establish an error-correction/data compression
connection, but some older modems may balk at such a connection. To solve 
this problem, use an alternate "dial prefix".

The normal dial prefix is ATDT. Sending ATDT345-6789 to the modem tells it 
to dial that number and connect with the remote modem. Your modem will try 
to negotiate speed and an error/correction/data-compression protocol (V.42
bis, MNP etc.) with the other modem. Some modems/software you call may NOT 
like this. If you are having trouble connecting with another modem, you can 
use a dialing prefix that disables error correction and data-compression.
┌────────────────────────────────┬─────────────────────┬──────────────────┐
│COMMAND                         │ DESIRED MODEM-      │ NEGOTIATE        │
│STRING                          │ TO-MODEM SPEED      │ PROTOCOL?        │
├────────────────────────────────┼─────────────────────┼──────────────────┤
│AT&Q5NIDT (uses default)        │ Negotiate           │ YES              │
│AT&Q6NIDT (try this next)       │ Negotiate           │ NO               │
│AT&Q5S37 = 11N0DT (1)           │ 14400 only          │ YES              │
│AT&Q6S37 = 11N0DT (1)           │ 14400 only          │ NO               │
│AT&Q5S37 = 10N0DT (2)           │ 12000 only          │ YES              │
│AT&Q6S37 = 10N0DT (2)           │ 12000 only          │ NO               │
│AT&Q5S37 = 9N0DT (3)            │  9600 only          │ YES              │
│AT&Q6S37 = 9N0DT (3)            │  9600 only          │ NO               │
│AT&Q5S37 = 6N0DT                │  2400 only          │ YES              │
│AT&Q6S37 = 6N0DT                │  2400 only          │ NO               │
│AT&Q5S37 = 5N0DT                │  1200 only          │ YES              │
│AT&Q6S37 = 5N0DT                │  1200 only          │ NO               │
│AT&Q6S37 = 1N0DT                │   300 only          │ NO               │
└────────────────────────────────┴─────────────────────┴──────────────────┘
NOTE: This character (0) is a zero, not the letter "O".

(1) V.32bis only    (2) v.32 Turbo and V.32bis  (3) All types of V.32

CONNECT messages / modem speed: S95=44 gives you full result messages, with
CONNECT messages reporting computer-to-modem speed. If you need CONNECT to
report modem-to-modem (carrier) speed, use S95=45. When operating a BBS, try
S95=3 and you will get only the CONNECT (carrier speed) message, with /ARQ 
for error-correction connections. Always set the "speed" in your program to 
the highest permissible computer-to-modem speed (see manual) for your par-
ticular modem. The modem will handle modem-to-modem speed.

COMMON PROBLEMS

If all else fails, it may be necessary to take your computer, with modem
installed, to a Radio Shack Service Center for diagnosis and possible
repair.

(dtc-07/30/93)