Cable Control-Comparator 1A12A3 and 1A12A14 Circuit Theory

TM 11-5820-695-35

voltage rating. The +5 volt output signal is coupled to

integrator A8 through diode CR12B and resistor R7.

2-42. Cable Control-Comparator

1A12A3 and

1A12A14 Circuit Theory (fig. 5-31 and 5-31.1)

Negative Pulse Generator. When 1NP is

logic one (approximately +3.5 volt), diode CR8 is

The integrated circuits used on cable control comparator

reverse biased, and Q2 is forward biased by +12 volts

1A12A3 are shown functionally in figure 5-31 for the

through R10. Current flow from -12 volts through R11,

synchronous mode and for 1A12A14 in figure 5-31.1 for

Q2 and RIO to +12 volts makes the voltage at the

the asynchronous mode. Figures 5-31 and 531.1 also

collector of Q2 positive which is clamped at -0.7 volt by

specify each integrated circuit type.

Figure 5-24

diode CR11. This is the low voltage output of the

provides a circuit diagram for each type of integrated

negative pulse generator. When 1NP is logic zero

circuit used in Radio Set AN/GRC-144. The complete

(ground), diode CR8 is forward biased, the emitter of

functional description of the cable control comparator is

transistor Q2 is at +0.7 volt and Q2 is reverse biased.

provided in paragraphs 25b for 1A12A3 and 2-5b.1 for

With Q2 off, current flow from -12 volts through resistor

1A12A14. Electrical operation of discrete piece parts for

R11, diode CR9 and zener diode CR10 drops the

the synchronous mode is provided in a through g below,

voltage at the collector of Q2 to -5 volts. This voltage is

and for both modes in h.

determined by the clamping action of diode CR9 and

zener diode CR10. The functions of resistor R12 and

Flip-Flops. The J and K inputs of flip-flops

capacitor C6 are the same as for resistor R6 and

A7A and A7B are maintained at logic one by connection

capacitor Cl (b above). The -5 volt output signal is

to the +5 volt supply voltage through resistors R1 and

coupled to differential integrator A8 through diode

R15.

CR12A and resistor R13.

Positive Pulse Generator. When 1PP is

Differential Integrator.

The differential

logic zero (ground) diode CR1 is forward biased and the

integrator is composed of capacitors C2, C3, C7, C8,

emitter of transistor Q1 is at logic zero (approximately

C9, resistor R14 and differential amplifier A8. Capacitor

+0.7 volt). Voltage division in resistor R3 and diode

C2 is a high frequency bypass. Capacitor C3 provides

CR6 provides the +1.4 colts at the base of Q1.

band-width limiting to prevent oscillation. Capacitors C7

Capacitor C4 filters this voltage. Transistor Q3 has -1.4

and C8 are supply voltage decouplers. Resistor R14

volts at the base which is provided by a voltage divider

and capacitor C9 form a long time constant signal

consisting of resistor R9 and diode CR7. The voltage is

feedback path. The feedback signal maintains the

filtered by capacitor C5. With transistor Q1 off, -12 volts

output signal and bridges over intervals when the

through resistor R4 forward biases Q3. Current flow

positive and negative pulse inputs are both absent.

from +12 volts through resistor R5, Q3 and resistor R4

Resistor R8 is an isolating resistor to couple the signal

to -12 volts produces voltage drops that make the

to test point E14.

voltage at the collector of Q3 negative. Diode CR5

clamps this voltage at -0.7 volt. This is the low voltage

Positive/Negative Clamp Detector.

output of the positive pulse generator. When 1PP is

Resistors R22 and R25 form a voltage divider which

high, diode CR1 is reverse biased. Transistor Q1 is

provides +0.75 volt as the reference voltage for the

forward biased by the positive voltage through resistor

positive clamp detector. Similarly resistors R26 and

R2 and its emitter is at approximately +2 volts. When

R27 provide -1V for the negative clamp detector.

Q1 is on, current flow from +12 volts through R2, Q1

Resistors R21, R23, and R24 form a voltage divider that

and R4 to -12 volts produces voltage drops that make

couples the signal output of A8 into the clamp detectors.

the voltage at the collector of Q1 positive. This voltage

The tapoff point at the center arm of resistor R23 is

is clamped at +0.7 volt by diode CR2. This is the

connected to the inputs of both clamp detectors and is

voltage at the emitter of Q3, therefore, Q3 is reverse

bypassed by capacitor C15.

biased. With Q3 off, current flow from + 12 volt through

R5, diode CR3 and zener diode CR4 to ground drops

Narrow Clock Pulse Generator and 48-

the voltage at the collector of Q3 to +5 volt. This

Channel Baud Generator. Resistors R16 and R17

voltage is determined by The clamping action of diode

connect the supply voltage into pin 13 of narrow clock

CR3 and zener diode CR4. Zener diode CR4 is

pulse generator A5. Variable resistor R17 and capacitor

protected against current surges by capacitor C1.

C10 set the time constant which determines the time

Resistor R6 provides additional current flow through

duration of the

zener diode CR4 to assure that the diode is operating at

its specified current rating to assure the specified zener

Change 1 2-81