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C Loopback Tests
133
displayed on your monitor. The TD and RD LEDs should flash when
a character is entered.
5. To exit the test, type the escape sequence +++AT and press EN-
TER. This puts the modem in online command mode. Then type
either AT&T or ATH to return to command mode.
6. Your modem passes this test if the data received on your monitor
are the same as the data entered from your keyboard. If different
data appear on your monitor, your modem is probably causing the
problem, though it could also be your computer. If your modem
passes this test, but you are receiving errors while on line, the re-
mote modem or the phone line could be at fault.
Remote Digital Loopback Test (V.54 Loop 2)
The remote digital loopback test tests the phone lines and the circuits
of both your modem and a remote modem. In this test, your modem
must be on line with another modem that is set up to respond to a re-
quest for remote digital loopback. (Note that some modems might not
support remote digital loopback or might have it disabled.) Data from
your computer or terminal is transmitted through your modem and over
the phone line to the remote modem, where it is then looped back to
your modem.
AT&T6
OK
Computer or Terminal Local MultiModem Remote MultiModem Computer or Terminal
Digital Analog DigitalAnalog
AT&T6
OK
UUUUUUUUU
UUUUU
Figure C-2. Remote digital loopback test.