provide sufficient power gain to drive loudspeaker LS201. The amplifiers operate only when the TEL-RAD-RAD/
SPKR switch is in RAD/SPKR position. When the TEL-RAD-RAD/SPKR switch is in either the TEL or RAD
position, battery voltage is removed from terminal 16 of component board A202, and a short circuit is placed
across the voice coil of loudspeaker LS201.
(1) Output signals of audio driver Q203 (para. 1-13c.(1)) are devebped across the primary (terminals 1 and
2) of T202 and are induced into the secondary of T202 (terminals 5, 6, and 7). The output of Q206 is applied
across one-half the primary of transformer T203 (terminals 1 and 2). The output of Q207 is applied across the
other half of the primary of T203 (terminals 3 and 2). Output signals devebped across the full primary of T203
(terminals 1 and 3) are induced into its secondary (terminals 4 and 5) driving loudspeaker LS201.
(2) Battery voltage is applied to Q206 and 0207 through emitter swamping resistors R215 and R216. Diode
CR202 and resistor R214 forma voltage divider which supplies a small forward bias. Diode CR202 also provides
improved temperature stabilization.
e. Ringing Circuits. Buzzer DS201 is normally in the circuit to reproduce the 20-Hz voltage generated by the
magneto in the local control unit. When the RINGER button is pressed, microswitch S203 disconnects buzzer
DS201 (and in A-, B- and C- models, the visual signal call lamp circuit) and places magneto G201 on the line.
Continued travel of the RINGER button shaft cranks the magneto to produce the 20-Hz voltage which causes a
response in the local unit buzzer (and in A-, B- and C- models, the call lamp). The BUZZER VOLUME control
mechanically controls the loudness of the buzzer.
In the later A-, B- and C- models, a radio frequency (RF) filter assembly is connected in
series with terminals of switch S203.
1-14. Battery Voltage Distribution, Remote Control Unit C-2328(*)/GRA-39
(figures FO-1 through FO-4)
The distribution of battery voltage depends on the position of the TEL-RAD-RAD/SPKR switch. The application
for each function is traced in the following paragraphs a. through d. OFF-ON switch S201 is considered to be at
ON throughout this discussion.
The following discussion applies to all models of Control, Radio Set C-2328(*)/GRA-39,
except where noted.
The application of the battery voltage is traced to a terminal of component board A201 or
a pin of connector P201. The application from these points is covered in paragraph 1-13.
a. RAD Position. With the TEL-RAD-RAD/SPKR switch in RAD position, battery voltage is applied to audio
driver Q203 during receive operation and to the preamplifier ((2201, Q202) and the tone generator (Q204, Q205)
during transmit operation.