TM 11-6625-596-45
2-5.
Preamplifier 1A3A1
output across 1A3A2CR4 (between pins C and F of
1A3A2P1) is proportional to the logarithm of the input at
pin S of 1A3A2P1. The dc output across 1A3A2CR4 is
applied through meter amplitude gain adjustment
either test microphone 1A2A4A4, MICROPHONE
CARBON terminal 1A4E1, MICROPHONE OTHER
1A4M1. Thermistor 1A3A2RT1 provides temperature
stabilization. Negative 30 volts is applied to assembly
electrical test panel 1A2A14. The microphone input to
1A3A2 at pin B of 1A3A4P1.
1A3A1 is applied through MICROPHONE LOAD switch
2-7.
B (1A4AT1 and 1A4AT2) to pin L of 1A3A1P1.
Assembly 1A3A8 consists of 18 load resistors and full-
amplifier 1A3A1Q1 is coupled through 1A3A1C4 to
wave bridge rectifier 1A3A8CR1 through 1A3A8CR4.
1A3A1Q2 and the output of 1A3A1Q2 is direct-coupled
to 1A3A1Q3. Feedback resistor 1A3A1R9andfeedback
a. Resistors 1A3A8R5, R6, and R7 form a
network 1A3A1R16, C5, R15, R12, and R5 compensate
load for testing hand generators. The load is connected
for variations in temperature and component aging to
to TEL LINE terminal L1 when HAND GENER-ATOR
maintain a constant gain of 60 dB. Filters 1A3A1C3,
button 1A4S6B is pressed. Resistor 1A3A8R19 is
R6, C7, and R13 provide power supply decoupling
added to the load when TEST button 1A4S5A is
between stages.
Negative 12 volts is applied to
pressed.
assembly 1A3A1 at pin C of 1A3A1P1. The output of
1A3A1 at pin A of 1A3A1P1 is applied through either
b. Resistors 1A3A8R2, R3, R10, and R12
LOW, CENTER, HIGH, or NARIROW BAND button
form voltage divider networks which provide minimum
(1A4S5B, C, D, or E) and filter 1A3FL1, FL2, FL3, or
operating currents for 2,400-, 5,300-, and 12,000-ohm
FL4 to meter amplifier 1A3A2. Fixed 16-dB attenuator
ringers. Resistors 1A3A8R1 and 1A3A8R4 also form a
1A3A1R18, R19, and R20 is inserted between filter
voltage divider for ringer tests. When one of the
1A3FL1 and 1A3A2, VALUE C attenuator (1A4AT3) is
RINGER buttons (1A4S6C, D, or E) is pressed, the
inserted between 1A3FL2 and 1A3A2, and VALUE D
voltage developed across 1A3A8R4 (pin E, 1A3A8P1) is
attenuator (1A4AT4) is inserted between 1A3FL3 and
applied through closed contacts of the pressed switch,
1A3A2.
and pin A of 1A3A8P1 to full-wave bridge rectifier
1A3A8CR1 through CR4. The dc output of the rectifier
2-6.
Meter Amplifier Assembly 1A3A2
at pin B of 1A3A8P1 is applied through contacts on
1A4S6 to meter 1A4M1 to give a visual indication that
the ringer test circuit is operating.
Assembly 1A3A2 amplifies the microphone output of
preamplifier 1A3A1 (para 2-5) or the simulated receiver
c. Resistor 1A3A8R11 is part of the insulator
output of transmission efficiency assembly 1A3A7 (para
When INSULATION RES-
2-8). The input to
1A3A2, which is
applied to
pin S of
ISTANCE button 1A4S6N is pressed, 1A3A8R11 is
1A3A2P1, is amplified by three common-emitter
series-connected with INSULATION RESIST-ANCE
control 1A4R13 and inserted between the output at pin 3
1A3A2Q3 is applied through 1A3A2C9 to METER
of 20-Hertz inverter 1A3A11 and bridge rectifier
SENSITIVITY CALIBRATE control 1A4R14 to
1A3A8CR1 through CR4.
complementary symmetrical output amplifier 1A3A2Q4,
Q5, and Q6. The symmetrical output of the output
d. Resistors 1A3A8R17 and R18 form a
amplifier is applied through 1A3A2C10 to full-wave
voltage divider for calibration of the sensitivity of meter
bridge rectifier 1A3A2CR1, CR2 and CR3, and
amplifier assembly 1A3A2.
The output of power
1A3A8CR4.
Diode 1A3A8CR4 is connected to
amplifier 1A3A4 (pin B, 1A3A4P1) is applied to
1A3A2CR1, CR2, and CR3 through pin F of 1A3A2P1,
1A3A8R17 and R18 in series, and the voltage across
contacts on 1A4S6, and pin C of 1A3A8P1. The dc
1A3A8R18 is applied to pin S of meter amplifier 1A3A2.
output of the rectifier is applied to logarithmic attenuator
e. Resistors 1A3A8R14, R15, and R16 form a
1A3A2CR4. Because of the conduction characteristics
of forward-biased germanium diode 1A3A2CR4, the
2-3