Testing; Local Analog Loopback - Epson ESC/VP21 User Manual

Fax/data modem

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4 - TESTING

The modem provides five testing features to identify fault location when transmission

quality is not good: local digital Ioopback, local analog loop back, local analog Ioopback

with self-test, remote digital loopback, and remote digital loopback with self-test.

These tests are initiated with the &Tn command described in Chapter 2.

The local analog loopback test checks the integrity of the local computer or terminal

and the local modem. During the test. the local modem internally loops data sent

from the local computer or terminal back to the same computer or terminal as

shown in Figure 4-1. During the test, data is not transmitted to the remote modem.

If characters are looped correctly during this test, both the modem and the local

computer or terminal are functioning correctly, If incorrect characters appear on

the screen, either the local computer or terminal or the local modem is in error.

To perform a local analog loopback, put the local modem in the command state.

If it is on-line, issue the escape command + + +, to return to the command state.

4 - TESTING

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