Section Il. OPERATING INSTRUCTIONS

C2, TM 11-6625-564-12

Section Il. OPERATING INSTRUCTIONS

2-3. Controls, Indicators, and Connectors

maintenance kit controls, indicators, and con-

The charts in a through d below list the

nectors and indicate their functions:

a. Test Unit Control and Indicator (fig. 22 ).

Control or indicator

Function

FUNCTION SELECT switch (four-position

Applies power to radio set and selects type of operation.

rotary)

Action

Switch position

OFF

Removes operating power from receiver-

transmitter,

Applies power to the receiver-transmitter

T/R

for transmission and reception; guard

receiver is not operative.

Same as T/R position except that guard

T/R+G

receiver is operative.

Same as T/R position except that the

ADF

aircraft automatic direction finder

system is in operation.

Controls audio level applied to headset.

AUDIO GAIN

potentiometer

Adjusts radio set main receiver sensitivity, When rotated

SENSITIVITY potentiometer

fully clockwise, it disables the squelch.

and SQ DIS switch

FREQ SELECT switches:

Selects portion of receiver-transmitter operating frequency

10-megacycle control

in 10-megacycle steps (first two digits).

(l8-position rotary switch)

Selects portion of receiver-transmitter operating frequency

l-megacycle control

in l-megacycle steps (third digit).

(l0-position rotary switch)

Selects portion of receiver-transmitter operating frequency

0.1megacycle control

in 0.05-megacycle steps (fourth and fifth digits).

(20-position rotary switch)

POWER RESET switch circuit

breaker

Connects and disconnects power to test unit.

(two-position)

Action

Switch

position

Removes +27.5 volts dc from test unit.

OFF

Applies +27.5 volts dc to the test unit.

RESET ON

Connects the HDSET H101A/U or the DUM MIC jacks

MIC SELECT switch

to the modulator and audio module of the receiver-

transmitter.

Action

Switch

position

Connects DUM MIC jacks to modulator

DUM MIC

and audio module of receiver-trans-

mitter. Disconnects audio amplifier No.

3 output from this module.

Connects audio amplifier No. 3 output to

HD SET

modulator and audio module of receiver-

transmitter. Disconnects the DUM MIC

jacks from this module.

Keys the receiver-transmitter.

PIT switch (three-position)

Action

Switch position

Grounds radio set keying relay, placing

radio set in transmitting condition.

XMIT lamp lights.

Ungrounds keying relay. Puts receiver-

OFF

transmitter in receive condition.

Places the receiver-transmitter in trans-

MOM ON

mitting condition and automatically

switches to OFF when released. XMIT

lamp lights.