Modem And Telephone Line Check; Step 1 - Motorola V.3400 User Manual

Fault Isolation Procedure

MODEM AND TELEPHONE LINE CHECK

Step 1

a. Configure the modem for LOCAL ANALOG LOOP
WITH TEST PATTERN. This terminates the local modem
telephone lines into 600 ohms and connects the local
modem transmit output amplifier back to its own receiver
through the AGC. Transmit input data from the terminal is
inhibited and is substituted with a V.52 test pattern.
b. This test checks operation of the local modem modulator
and demodulator circuitry and should be attempted at both
local and remote sites if operators are available.
c. When random errors are present, the TEST PATTERN
ERRORS display counts receive errors.
d. If the circuitry is working properly, the front panel indica-
tors show the following:
e. Configure the modem for LOCAL ANALOG LOOP to
switch the transmitter back to its normal data input.
f. If the transmit data input is in a mark hold condition, both
the TD and RD indicators should remain off.
g. If the transmit data input is in a space hold condition, both
the TD and RD indicators should come on. All other indi-
cators should remain the same.
h. If the indicators are correct, the modem is probably oper-
ating correctly.
i. If the preceding tests were not successful, call Technical
Services.
D-2 V.3400