Circuit Functioning-continued

TM 11-5820-498-35

vided through the CX-4656/GRC (pins EC)

(1) Before the RF signals are received from

and relays K1 and K2 to the 12.5-15 volt batter

either distant radio station, the relay site re-

in receiver-transmitter No. 2.

ceiver-transmitters are in standby mode. Under

(d) With the transmitting circuits in re-

t h i s situation, the output transformers, in

ceiver-transmitter No. 2 in transmit mode by the

A25/A55 in No. 2 and T5001 in No. 3, are

operations of K1 and K2, speech signals can now

grounded through contacts of their associated

be applied from T5005 in receiver-transmitter

squelch relays. Thus, no signals can pass between

the relay site receiver-transmitters.

No. 3 through the CX-4656/GRC (pins E-C) and

the transmitting circuits in receiver-transmitter

(2) When a signal including the 150-Hz

No. 2 to the antenna for transmission to radio

squelch signal is received at receiver-transmitter

station. No.1.

No. 2, it is applied through RF-IF amplifiers and

(e) When radio station No. 4 ceases keying

the discriminator to receiver audio amplifier

its transmitter, receiver-transmitters No. 3 and 2

A25/A55.

(3) From the discriminator, the 150-Hz

go into standby condition ((1) above).

squelch signal is applied to squelch relay control

(f) Diode CR1 in the C-E circuit of the

A24/A54. A24/A54 then provides a closed circuit

CX-4656/GRC is provided to keep the two differ-

ent battery potentials separated when the re-

to operate relay K3. When K3 operates, contacts

ceiver-transmitters No. 3 and 2 are in standby.

8-3 remove the short from output transformer in

A25/A55 ((1) above).

The diode prevents receiver-transmitter No. 2

(4) Simultaneously, ground on the output

from going into transmit mode by the operation

transformer in A25/A55 is provided through

of K1 and K2. Under this condition, the circuit

function switch S1 and applied through diode

performs as follows:

CR2 in the CX-4656/GRC and through receiver-

NOTE

transmitter No. 3 relays K405 and K401 to the

If the CX-4656/GRC cable connects to the

25-volt battery. Thus, contacts 4-7 of K1 provide

receiver-transmitters shown in figure 4-8

operating power continuity to receiver-transmit-

diode CR2 in the C-E circuit would perform

ter No. 3 transmitting circuits by the operation of

the operations described for CR1 below.

relays K405 and K401.

(5) With the transmitting circuits in re-

1. When receiver-transmitter No. 2 is

ceiver-transmitter No. 3 in transmit mode, speech

connected to another RT-505/PRC-25 or

signals can now be applied from receiver-trans-

RT-841/PRC-77, a squelch signal received by No.

the

through

2 A25/A55

mitter No.

3 provides a simple ground to the battery in No. 2

C X - 4 6 9 6 / G R C to receiver-transmitter No. 3

which causes relays K1 and K2 to operate for

transmit circuits, and to the antenna for trans-

transmission (fig. 4-3 and para 2-7 b(4)).

mission to radio station No. 4.

(6) When radio station No. 1 ceases keying

2. However, when an RT246(*)/VRC

its transmitter, receiver-transmitters No. 2 and 3

or RT-524(*)/VRC is used as receiver-transmit-

go into standby condition ((1) above).

ter No. 3, there are two different battery poten-

(7) When radio station No. 4 keys its trans-

tials, 12.15 volts in No. 2 and 25 volts in No. 3.

mitter and transmits its signals, the operation of

If there were no diode CR1 in the CX-4656/GRC

the circuits in receiver-transmitters No. 3 and 2

when the receiver-transmitters are in standby,

are accomplished as follows:

the two batteries would be connected in series (B,

(a) When a signal including a squelch

fig. 4-8). When two such opposing potentials

signal (150-Hz or noise) is received at receiver-

meet, a voltage difference (between 10 and 12.5

transmitter No. 2, it is applied through the re-

volts) would be sufficient to operate K1 and K2

ceive circuit.

into transmit mode in receiver-transmitter No. 2.

(b) In the receive circuit, the squelch sig-

nal is applied to squelch control A5200, causing

3. The diode in CX-4656/GRC preven

squelch relay K5002 to operate. When K5002 oper-

this extra voltage from operating K1 and K2. The

ates, a ground is provided through contacts 2-5

remaining voltage is blocked because the poten-

of K505, CR303 (in RT246(*)/VRC), or CR351

tial (which takes on the polarities of the 25-volt

(in RT-524(*)/VRC), and the CALL lamp to the

battery) would apply a negative potential to the

25-volt battery.

anode of the diode. Thus, no current can flow

(c) At the same time, the ground is pro-

operate K1 and K2 in receiver-transmitter No. 2.

2-10