SQUELCH SWITCH S9106

TM 11-5820-670-30

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

The homing indicator vertical (course) needle is controlled by the homer course voltage from the

homer assembly. The homer course voltage is coupled from the receiver-transmitter to pin t of

connector J9101. From pin t, the course voltage is connected through contacts 1 and 2 on the rear

wafer of S9105B. From contact 1, the homer course voltage is connected through pin (s) of

connector J9101 to the homing indicator vertical needle ( + ) input. The vertical needle (-) input is

returned directly to the homer assembly in the receiver-transmitter.

SQUELCH SWITCH S9106

The radio set has three squelch modes, squelch disable (DIS), carrier squelch (CARR), or tone

squelch (TONE). Squelch mode is selected by SQUELCH switch S9106 on the control unit. When

S9106 is set to DIS, the radio set will receive all fm signals within its frequency band regardless of

signal strength or the presence or absence of tone modulation.

VOL CONTROL R9103

VOL control R9103 is a 250 ohm potentiometer, wired in series with the received audio signal to control

the audio volume.

The received audio signals from contact 1 of S9105C front are coupled through the wiper arm of R9103

to the aircraft interphone amplifier.

Resistor R9104 prevents the audio output from being reduced to zero when VOL control is turned

maximum counterclockwise.

FREQUENCY SELECTOR CONTROLS S9101, S9102, S9103, and S9104

The radio set is tuned through a frequency range of 30.00 MHz to 75.95 MHz in 0.05 MHz steps.

Tens MHz selector S9101 changes frequency of radio set in 10 MHz steps.

Units MHz selector S9102 changes frequency in 1 MHz steps.

Tenths MHz selector S9103 changes frequency in 0.1 MHz steps.

Hundredths MHz selector S9104 changes frequency in 0.05 MHz steps.

The frequency selector switches in the control unit develop a frequency selection code which controls

the operation of tuning circuits in gearbox assembly of the receiver-transmitter and tuning circuits of

the antenna coupler. These switches are part of a five-wire, open-seeking, reentrant system that

controls motors in gearbox assembly A9700.

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