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MultiModemII User Guide
92
3. Type AT&T1 and press ENTER. This places your modem in analog loopback
mode in the originate mode. A CONNECT message should appear on your dis-
play. The modem is now out of command mode and in a pseudo-online mode.
4. Note that the CD and TM indicators are on. If they are not on, there is a defect in
your modem.
5. Enter characters from your keyboard. For this test, typing multiple uppercase U
characters is a good way to send an alternating test pattern of binary ones and
zeros. The characters entered should be displayed on your monitor. The TD and
RD LEDs should flash when a character is entered.
6. To exit the test, type the escape sequence +++AT and press ENTER. This puts the
modem in online command mode. Then type either AT&T or ATH to return to
command mode.
7. Your modem passes this test if the data received on your monitor are the same
as the data entered from your keyboard. If different data appear on your moni-
tor, your modem is probably causing the problem, though it could also be your
computer. If your modem passes this test, but you are receiving errors while on
line, the remote modem or the phone line could be at fault.
Note: You can also start and stop an analog loopback test by using the front panel
LCD and buttons. See “Diagnostic Options Trunk” in Chapter 3.
Remote Digital Loopback Test (V.54 Loop 2)
The remote digital loopback test tests the phone lines and the circuits of both your
modem and a remote modem. In this test, your modem must be on line with another
modem that is set up to respond to a request for remote digital loopback. (Note that
some modems might not support remote digital loopback or might have it disabled.)
Data from your computer or terminal is transmitted through your modem and over
the phone line to the remote modem, where it is then looped back to your modem.
Computer or Terminal
Digital Analog
AT&T6
OK
Local MultiModem Remote MultiModem Computer or Terminal
DigitalAnalog
AT&T6
OK
UUUUUUUUUUU
UUU
Figure C-2. Remote digital loopback test.
Test procedure
1. Arrange to have &T6 set on the remote test modem.
2. Open your communications software and go into terminal mode. Type AT and
press ENTER; you should get an OK message. Type AT\N and press ENTER to dis-
able error correction.