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C Loopback Tests
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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 re-
mote 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
OK
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
OK
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
OK
message
from your modem (if responses are enabled), your modem is placed
in digital loopback mode.