TM 11-5805-356-34-1
emitter follower A2Q6, the low voltage devel-
c. Rectifier A2CR1. The rectifier converts the
oped at the collector of the transistor is coupled
ac break-in signal to dc. The ac voltage coupled
through diode A2CR3 and isolating resistor A2-
through capacitor A2C8 is developed across re-
R23 to the base of transistor A2Q9. The nega-
sister A2R16. Diode A2CR1 acts as a positive
tive-going signal changes the state of the multi-
clamp, causing a positive dc voltage proportional
vibrator, causing transistor A2Q9 to conduct and
to the average value of the incoming signal to be
transistor A2Q8 to cut off.
applied to the base of transistor A2Q5.
(2) With the multivibrator set, the low
d. Dc Amplifier A2Q5. The dc amplifier am-
voltage at the collector of A2Q8 is applied to the
plifies the voltage applied to its input. The out-
base of buffer amplifier A2Q7, causing A2Q7 to
put voltage is developed across collector load re-
conduct. The conduction of A2Q7 makes the col-
sistor A2R20. Stage gain is determined by the
lector more positive, and this positive voltage is
setting of MODE ONE-MODE TWO switch
applied through diode A2CR4, contacts 3 and 1
S10. The gain is established by the emitter bias,
of switch S5A, and resistor A1R6 to the delay
which is provided by the voltage across resistor
amplifier in the send circuit (para 2-10b). The
A2R19 in voltage divider A2R18, A2R17, and
positive signal locks the send circuit to the space
A2R19. For the MODE TWO position of switch
state, equivalent to a ring signal, causing the
S10, resistor A2R18 is shorted out, providing a
alarm to sound at both TH-22/TG units.
more positive voltage across resistor A2R19.
(3) The low voltage existing at the collector
e. Time-Delay and Integrator A2CR2. This cir-
of A2Q8, when the multivibrator is set, is also
cuit prevents spurious signals from actuating the
applied to the base of transistor A2Q12 through
break-in circuit by requiring a capacitor to charge
contacts 7 and 5 of switch S5A and resistor A2-
up to the turn-on voltage of transistor A2Q6.
R40. Transistor A2Q12 constitutes one-half of
Capacitor A2C10 charges through resistor A2R-
AND gate A2Q12-A2Q13 in the carrier-suppres-
21, building up the required voltage to turn on
sion circuit (para 2-13). With a positive voltage
transistor A2Q6 in 0.5 second or more. Local
applied to the base of transistor A2Q12, the
generation of the break-in signal, which requires
AND gate is disabled, so that the carrier-sup
the operating of the BREAK IN switch, connects
pression circuit is locked out once the break-in
a short circuit across capacitor A2C10, inhibiting
circuit multivibrator is set.
further signal processing by the break-in circuit
(4) Once set, the multivibrator remains set
in the unit sending the break-in signal.
until reset manually. Operation of the RESET
f. Emitter Follower A2Q6. With an incoming
switch connects the base of transistor A2Q9 to
break-in signal, this circuit applies a forward-
+18 volts. The positive voltage reverse-biases the
biasing voltage for diode A2CR3, causing multi-
transistor, causing the multivibrator to switch
vibrator A2Q8-A2Q9 to change state if it is not
state so that A2Q8 again conducts and A2Q9 is
inhibited by the BREAK-IN DISABLE strap or
cut off.
the output of AND gate A2Q12-A2Q13. The in-
(5) The multivibrator can be disabled in
put is direct-coupled to the base of transistor A2-
two ways so that it will not set in response to
Q6. Resistor A2R22 is the emitter load across
a break-in signal. If the BREAK-IN DISABLE
which the output voltage is developed. When a
strap is connected, the collector of transistor A2-
break-in signal is received, transistor A2Q6 con-
Q8 is connected to the +18-volt bus, preventing
ducts (when sufficient voltage is developed
the collector voltage from changing and the mul-
across capacitor A2C10), forward-biasing A2CR3
tivibrator from setting. The second way is when
and allowing the emitter follower to turn on
the carrier-suppression circuit (para 2-8) is sup-
transistor A2Q9.
pressing the carrier. At that time, transistor A2-
g. Multivibrator A2Q8-A2Q9 and Buffer Am-
Q10 is cut off. This ties the base of transistor
plifier A2Q7.
A2Q8 to 0 volt through diode A2CR5 and re-
(1) During normal operation, while the
sistor A2R34, inhibiting the setting of the multi-
break-in signaling feature of the TH-22/TG is
vibrator by preventing transistor A2Q8 from
not being used, multivibrator A2Q8-A2Q9 is in
being cut off.
the reset state. In this state, transistor A2Q8 is
conducting and transistor A2Q9 is cut off. As-
2-8. Carrier-Suppression Circuit
suming that the mode of operation in use permits
the break-in circuit to be effective, the reception
of the break-in signal causes the multivibrator to
a. Delay Amplifier A2Q14. Delay Amplifier
set. When the break-in signal has turned on
A2Q14 controls the time for which a mark fre-
2-11
Previous Page
