Appendix C: Loopback Tests; Local Analog Loopback Test (V.54 Loop 3) - Multitech MultiModem MT5600ZDX User Manual

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Appendix C: Loopback Tests

Introduction

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.

Note: 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.

C Loopback Tests

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