Radio Set Control C-1439/U

part of a communication system that con-

bleeder resistor R1806 and terminals 10

sists of Receiver-Transmitter Group OA-

and 12 of P1801. Resistive networks with-

2648/VRC-24 and Radio Set AN/GRC-5,

in the RT-441/TRC-68 form a voltage di-

radio interphone switch S1504 functions

vider circuit that provides +125 volts from

as follows:

terminal 10 of P1801 to ground and -30

(1) On the RAD INT position, the radio

volts from terminal 12 of P1801 to ground.

interphone switch connects AN/

This circuit is protected by fuse F1807.

VRC-24 and AN/GRC-5 headset

Filtering is provided by reactors L1803

(through contacts 4 and 1 of S1504B

and L1804 and capacitors C1804 and C1805.

rear) and speaker (through con-

Capacitor C1803 and coil L1803, connected

tacts 8 and 5 of S1504B rear) audio

in parallel, present a high impedance to the

to terminal A and L on AUDIO jacks

120-cps components of the full-wave recti-

J1502 and J1503. In this position,

fier output, for improved filtering action.

push-to-talk transmission is per-

mitted on Radio Set AN/VRC-24

88. Radio Set Control C-1439/U

and the AF Amplifier AM-65/GRC

(fig. 30)

(part of the AN/GRC3-8 series)

interphone amplifier through con-

Radio Set Control C-1439/U permits

tacts 9 and 12 of S1504B rear and

remote control and operation of Receiver-

contacts 4 and 1 of S1504A.

Transmitter Group OA-2648/VRC-24 or

(2) On the INT position, switch S1504

OA-2649/TRC-68. The push-to-talk cir-

applies RT-323/VRC-24 and AN/

cuits of associated communication equip-

GRC-5 headset and speaker audio

ment such as Radio Set AN/GRC-3 through

to AUDIO jacks J1502 and J1503

-8 can also be controlled from this unit.

in the manner described in (1)

a. The C-1439/U contains controls that

above (except that contacts 3, 7,

duplicate the function of similar controls

and 11 of S1504B rear make con-

on the front panel of the rt unit. The func-

tact). In this position, the switch

tion of CHANNEL selector switch, S1503

permits push-to-talk transmission

is covered in paragraph 84. The functions

on Radio Set AN/GRC-5 interphone

of SQUELCH control R1501, SQUELCH

only.

DISABLE PUSH switch S1501, SQUELCH

OFF switch S1502, and CALL LIGHT lamp

(3) In the RAD position, switch S1504

I1501, are covered in paragraph 42. The

applies only RT-323/VRC-24 audio

function of POWER control S1505 is

output to AUDIO jacks J1502 and

covered in paragraphs 80 and 81. The

J1503. The headset and speaker

PHONE VOLUME and the SPEAKER VOL-

audio input terminals to the rt unit

UME controls, which consist of resistors

are terminals J and F of J1501.

R1502 and R1506, and resistors R1503 and

Microphone audio and push-to-talk

R1504, control the headset and speaker

control circuits are switched to

audio levels at terminals A and L, respec-

ouput terminals a and U of J1501,

tively, of AUDIO jacks J1502 and J1503.

and transmission on Radio Set

Both volume control circuits are similar

AN/VRC-24 only is permitted.

to the front panel volume control circuits

d. When the C-1439/U is used with Re-

(para 45).

ceiver-Transmitter Group OA-2649/TRC-

b. When the C-1439/U is used with

68, or when the retransmit cable used with

Receiver-Transmitter Group OA-2648/

Radio Set AN/VRC-24, Special Purpose

VRC-24, a pilot lamp I1502 is connected

Cable Assembly CX-4498/U, is not con-

as shown in figure 24. When the C-1439/

nected to the AN/GRC-5 equipment, radio

U is used with Receiver-Transmitter

interphone switch S1504 functions as fol-

Group OA-2649/TRC-68, the pilot lamp is

lows:

connected through rt case wiring to

(1) On the RAD INT position, radio

POWER indicator lamp I1801 (fig. 29).

interphone switch S1504 switches

c. When control C-1439/U is used as

the headset and speaker output