CONTROL, RADIO SET C-7088/ARC-131 FUNCTIONING-continued

TM 11-5820-670-30

1-59. CONTROL, RADIO SET C-7088/ARC-131 FUNCTIONING. (CONT)

When SQUELCH switch S9106 is set to TONE, the ground at contact 7 is connected through contact 8

to contact 9 on the rear wafer of S9105A. This ground is applied to pin X of connector J9101 only when

the mode control switch is set to T/R or RETRAN position. From pin X, the squelch tone ground is

connected through the interconnecting wiring and is used to operate the tone mode relays in the

audiofrequency amplifier assembly.

Tone mode relays K5503, K5504, and K5505 (not shown) perform the required switching for the

squelch filter and receiver-squelch amplifier. When the received signal is modulated by a 150 Hz

tone, the receiver-squelch amplifier tone rectifier circuit will unsquelch the receiver-audio amplifier.

Homer operate voltage is also applied from contact 7 of S9105A front through current limiter R9101, to

pin GG of connector J9101. This voltage is used to operate the homing indicator flags. Operation of

the flags depends on the ground return. This ground return is provided by the squelch relay in the

audiofrequency amplifier when sufficient signal is received to cause unsquelching. The ground is

connected, as in RETRAN operation, from the audiofrequency amplifier, through interconnecting

wiring to pin Y of control unit connector J9101.

As in RETRAN operation, SQUELCH switch S9106 must be set to either CARR or TONE position. From

J9101 pin Y, ground is connected to contacts 11 and 12 of S9106. With switch S9106 positioned to

CARR or TONE, contacts 11 and 12 are connected to contact 1 which is connected to contact 9 on the

rear wafer of S9105B. In HOME position, contacts 9 and 10 are connected and the ground is applied to

pin FF of connector J9101 of the control unit and then to the homing indicator to operate the flags.

The homing indicator horizontal (signal strength) needle is controlled by the signal voltage from the

homer assembly. The signal strength voltage is coupled from the receiver-transmitter unit to pin MM

of control unit connector J9101. From pin MM, the signal strength voltage is connected to contact 6 on

the rear wafer of S9105B.

In HOME mode, contact 6 connects to contact 5. From contact 5, the signal strength voltage is

coupled through pin NN of J9101 to the homing indicator. The homing indicator horizontal needle

negative terminal is returned to the homer assembly in the receiver-transmitter.

1-66