DCB SM-56 Troubleshooting Manual

DCB, Inc.
2949 CR 1000 E
Dewey, Illinois

61840

217.897.6600 Tel

800.432.2638 Toll Free

217.897.1331 Fax
www.dcbnet.com

SM-56 Security Dial-Up Modem

Application Troubleshooting Guide

A step-by-step configuration to implement an encrypted dial-up connection using two
SM-56 units is shown starting on page 6 of the manual. The following are points at which
problems may occur.

1. If your attached device does not provide a DTR signal, you need to issue the
command AT&D0 after the ATS0=1 on the answering modem.

2. Both modems need the same key. If you use the auto-generated random key, then
you should only generate the key on one modem and write down that key to enter
it in the other modem. Auto-generating random keys on both modems will result
in both modems having different keys and won't work.

3. The commands entered after the AT+K command in the answer configuration of
the sample are entered blindly. That is, after the AT+K command, you only see
“OK” after entering the remainder of commands (from AT+E1 to AT&Y0 on the
list).

4. If the device connected to the answer modem is streaming data, the call will be
aborted. This is characteristic of all dial-up modems.

5. If the device connected to the answer modem echoes data the modem will not
answer. To correct this, issue the command ATQ1&W to the answer modem. This
will quiet the modem result codes so that there is no data to echo. You will not see
an “OK” after you issue this command.

6. The modem DTE speed is set by dip switches. Insure that you have that speed
match your devices. See p. 11 of the manual. The default setting is 57,600.

7. If the modems connect but you are still having problems, suspect wiring issues.
See p. 10 of the manual for the modem's interface description.

The SM-56 modem is shipped with several wiring adapters and a straight through line
cord. Combining the DIRECT PC and REMOTE PC adapters with the line cord between
them provides a null modem cable to connect directly to a PC for initial configuration.
Combining the DIRECT PC and REMOTE PC 25 adapters with the line cord between
them provides a cable to make the modem appear as a standard 25 pin modem DCE
interface.