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MT3334HD8 User Guide
54 CommPlete Communications Server
Introduction
Each time you power up the MT3334HD8, it performs an automatic self-test to ensure proper operation.
The MT3334HD8 also has three diagnostic tests: local analog loopback, digital loopback
(remote/automatic), and digital loopback (local/manual). These ITU-T V.54 loopback tests isolate
telephone circuit and transmission problems.
In a loopback test, data from your computer loops through the circuits of your modem and/or a remote
modem before it appears on your monitor. When the loop has been completed, the data on your PC’s
monitor should match the original data.
The local analog loopback test allows you to verify that the modem’s transmitter and receiver circuits are
functioning properly.
The local digital loopback allows you to verify that the local computer or terminal, the two modems, and
the transmission line between them are functioning properly.
The remote digital loopback test allows you to verify that the remote computer or terminal, the remote
modem, the serial ports, the telephone line, and the local modem are functioning properly.
Note: All loopback tests operate at all speeds except 300 bps.
Other tests are initiated with the MultiModemManager software, as explained in the MultiModemManager
Owner's Manual
.
Local Analog Loopback Test (V.54 Loop 3)
In this test, data from your computer or terminal is sent to your modem’s transmitter, converted into
analog form, looped back to the modem’s receiver, converted into digital form, and then sent to your
monitor for verification. No connection to the phone line is required. See Figure 2.
Computer or Terminal
UUUUU
UUUUU
Type ATU0 or ATU1 in
terminal mode; hit ENTER.
Local MultiModem
Digital Analog
Figure 2. Local analog loopback test.
Test procedure
1. Connect the modem to your computer. Using your communication software, set the desired baud
rate.
2. Type ATU or ATU0 and press ENTER. This places your modem in analog loopback mode in the
originate mode. A
CONNECT message should appear on your display. The modem is now out of
command mode and in a pseudo-online mode.