Functioning of Local Control Unit C-2329(*)/GRA-39

TM 11-5820-477-30

1- 15. Functioning of Local Control Unit C-2329(*)/GRA-39 (figures 1-5 and 1-6)

NOTE

The following discussion applies to all models of Control, Radio Set C-2329(*)/GRA-39,

except where noted.

a. Telephone Operation Between Sites.

(1) Ringing. Signaling the operator at the remote site requires that the RINGER button be pressed and

released rapidly several times; this action activates magneto G101 to generate a ringing signal. When the

RINGER button is pressed, switch S103, which normally connects buzzer DS101 (and in A-, B- and C- models, a

call lamp signal) to audio line transformer T101, is actuated to connect the magneto to T101. The ringing signal is

coupled through T101, through the line to the remote site. Incoming ringing signals are coupled through T101 to

activate buzzer DS101. In A-, B- and C- models, incoming ringing signals are also applied to the call lamp control

relay to activate the call lamp visual signal. For operation of DS101, TEL-REMOTE-RADIO switch S102 may be

in any position; however, it must be held at the TEL position for the operator at the remote site to hear the local

operator's voice.

(2) Telephone communication. With the TEL-REMOTE-RADIO switch held in the TEL position, transmitted

voice signals generated in the microphone of the H-138/U are amplified by audio amplifiers Q101 and Q102 in the

preamplifier and are coupled through T101 through the line to the remote site. Incoming voice signals from the

remote site are coupled by T101 to the H-138/U earpiece through switch S102.

b. Operation of Radio Set From Local Control Unit.

(1) Transmitting. With the TEL-REMOTE-RADIO switch held in the spring-loaded RADIO position (with the

handset push-to-talk switch pressed), voice signals developed in the handset microphone are connected through

switch S102, transformer T102, and filter FL104 to the radio set transmitter. Relay K101 is energized and, in turn,

keys the radio set transmitter.

(2) Receiving. With the TEL-REMOTE-RADIO switch in REMOTE or held in the RADIO position, signals

from the radio set are applied directly through switch S102 to the handset earpiece.

c. Operation of Radio Set From Remote Control Unit. With the TEL-REMOTE-RADIO switch in the REMOTE

position, the local control unit couples the signals from the remote control unit to the radio set transmitter and the

signals from the radio set receiver to the remote control unit.

(1) Transmitting. Voice and 3,900-Hz signals present at the LINE binding pests are coupled through T101 to

filters FL101 and FL102, respectively. Filter FL102 is a series-tuned filter which passes only a 3,900-Hz signal.

Filter FL101 is a parallel-tuned filter, which provides rejection to the 3,900-Hz signal and allows voice signals to

pass. Filter FL102 applies the 3,900-Hz signal to resonant relay amplifier (Q103, Q104, and Q105). The

3,900-Hz signal is amplified, rectified, filtered, and provides a direct current (de) voltage output to energize relay

K101. When relay K101 is energized, it applies a ground circuit in the radio set which causes the transmitter to be

keyed. This condition allows voice signals from the remote control unit, present at filter FL101, to be applied

through relay K101 to the attenuator. The attenuator reduces the strength of the voice signals approximately the

same amount as they were amplified in the remote control unit preamplifier. Signals present at the output of the

attenuator are then coupled through switch S102, transformer T102, and filter FL104 to the radio set transmitter.

Filter FL104 provides further rejection to the 3,900-Hz tone signal.

1-13