Multi-Tech Systems MT5600ZDX ユーザーズマニュアル

Each time you turn on your modem, it performs an automatic self-test to ensure
proper operation. Your modem also has three diagnostic tests: local analog
loopback, remote digital loopback, and local digital loopback. 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.

: All loopback tests should be run at 9600 bps without error correction.

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.

Figure C–1. Local analog loopback test.