Multitech MTA128ST-USB Betriebsanweisung PDF herunterladen (Seite 59)

Appendix C - Loopback Tests

Local Digital Loopback Test (V.54 Loop 2)

The local digital loopback test is identical to the remote digital loopback test with one exception.

Instead of using your modem to signal a remote modem to place itself in digital loopback mode, your

modem is placed in digital loopback mode while the remote modem is not. Data is entered and

transmitted from the remote modem, sent across the phone line to your modem, and looped back to

the remote modem.

UUUUUUUUU

UUUUU

Computer or Terminal Local MultiModem Remote MultiModem Computer or Terminal

Digital Analog DigitalAnalog

AT&T3

Figure C-3. Local digital loopback test

Test Procedure

1. Open your communications software and go into terminal mode. Type AT and press ENTER;

you should get an

message. Type AT\N and press ENTER to disable error correction.

2. Dial the remote modem and establish your online connection.

3. Type the escape sequence +++AT and press ENTER to bring your modem into online

command mode.

4. Type AT&T3 and press ENTER. Once you receive an

message from your modem (if

responses are enabled), your modem is placed in digital loopback mode.

5. Have someone enter data from the remote keyboard. For this test, typing multiple uppercase

characters is a good way to send an alternating test pattern of binary ones and zeros. The

data received by your modem enters its analog receiver, is converted to digital data, is

reconverted into analog, and then is transmitted back to the remote modem. Your modem

passes this test if the data received on the remote monitor is the same as the data entered

from the remote keyboard.

6. To exit the test, type the escape sequence +++AT and press ENTER. This puts the modem in

online command mode. The modem should respond with an

message. If you wish to stay

on line with the remote modem for normal data transmission, type AT&T and press ENTER to

exit the test, then type ATO and press ENTER to return on line. If you wish to terminate the

call, type ATH and press ENTER to hang up.

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Multitech MTA128ST-USB Betriebsanweisung Seite 59