TM 11-7025-234-23
d. Remote Loopback Board (A8) Jumpers. A remote dc loopback is initiated by
sending a 1.92 kHz tone to the remote site. A remote audio loopback is initiated
by sen d ing a 2.4 Hz tone. The transmit carrier is off while tone is sent. Sending
both tones simultaneously clears the loopback. The duration of time the tones are
sent for each of the three commands is determined by a plug jumper. This jumper
(FAST)= 1.06 SEC
F
N (NORMAL)= 2.13 SEC
S (SLOW)= 4.27 SEC .
Remote Loopback Board (A8) Plug Jumper
Rear Panel 1/0 Board (A9) Jumpers. The domestic rear panel and associated
e.
connectors (fig. 1-11) are part of a plug-in circuit board assembly which installs
in modem board slot A9. Jl, a 25-pin connector, is the standard interface
connector supplying input/output data, control, status, and timing interface
signals between the modem and the data terminal equipment. J2 thru J4 are
identical to J1 and are used for channels 2 thru 4 of the multiplexer option. J5,
a 25-pin connector, is normally used to terminate the telephone transmit and
1-18
