Figure 1-10. Remote Loopback Board (A8) Plug Jumper

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

(fig. 1-10) will normally be in the 2.13 second position.

(FAST)= 1.06 SEC

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

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