Figure 1-11. Domestic 1/0 Board (A9), Rear Panel Connectors

TM 11-7025-234-23

Domestic 1/0 Board (A9), Rear Panel Connectors

receive lines. A cable assembly is provided to connect J5 to the telephone lines.

J6 is a 15-pin connector, provided for use with the Alternate Voice/Data. J7 is

used for secondary channel interface connection. The red and green wires connect

to the V.29 modem transmitter output, and the yellow and black wires connect to the

V.29 modem's receiver input. Terminal board 1 has five screw terminals which may

also be used for connecting the telephone lines if desired. Figure 1-12

illustrates the 1/0 interface cabling. The interface is compatible with EIA

RS-232C and (CCITT V.24) low level input/output interface and interface exchange

requirements. Table 1-3 lists and describes each interface signal. There is one

active component on the domestic 1/0 board, an operational amplifier in the

transmit audio path, which provides transmit pre-emphasis and a selectable 1 dB

lowering of the transmit level capability. The two audio line transformers are

also mounted to the 1/0 board and interface to it. There is a series of patch or

solder jumpers (fig. 1-13) provided on the 1/0 board which are accessible on the

solder side. These are described in table 1-4.

1-19