Alarm-Monitor 2A12 Block Diagram Description

TM 11-5820-695-35

predetermined level, the dc voltage applied to the base

2-24.

Alarm-Monitor

2A12

Block

Diagram

of Q5 is not sufficient to keep Q5 conducting. With Q5

Description (fig. 5-20)

turned off, Q6 turns on and Q7 turns off. For this

condition, a high impedance path to ground is applied to

Alarm-monitor 2A12 receives the traffic,

the traffic normal indicator lamp and a low impedance

carrier (if), and synthesizer monitor signals and controls

path to ground is applied to the traffic alarm indicator

associated alarm indicators on meter panel assembly

lamp. Consequently, the TRAF indication changes from

2A15A2. Depending upon the signal level received, the

green to red. Also with Q7 turned off, the Q7 output dc

associated indicator lights either green (normal

voltage is high enabling the OR gate which causes 023

indication) or red (alarm indication). Alarm-monitor

to turn on. With Q23 turned on, a receiver summary

2A12 also contains a summary alarm circuit which is

alarm indication is applied to r-1054(P)/GRC-144(V).

enabled when any one of the alarm condition occur.

The traffic monitor signal is received from af-rf amplifier

(2) The synthesizer monitor signal is received

2A4 and indicates the composite pcm and orderwire

from electrical frequency synthesizer 2A14 and is

signal level at the output of the R-1467(P)/GRC-144(V).

applied directly to Schmitt trigger circuit Q14 and Q15.

The synthesizer monitor signal is received from

Circuit operation is identical to that described above for

electrical frequency synthesizer 2A14 and indicates if

the traffic monitor circuit. If the synthesizer signal

the signals from radio frequency oscillator 2A14A1 and

exceeds a predetermined dc level, the SYNTH LOCK

standard radio frequency oscillator 2A14A7 are phase

indicator on 2A15A2 lights green (normal indication). If

locked. The carrier (if) monitor signal and associated

the synthesizer monitor signal is below the

reference signal are received from 70 MHz intermediate

predetermined level, the associated indicator lights red

frequency amplifier 2A5 and indicate if the 70 MHz if

(alarm indication) and, in addition, the summary alarm

carrier signal in 2A5 is above a predetermined level.

circuit is enabled.

The TRAF, SYNTH LOCK, and CARR IF

(3) The carrier (if) monitor signal is received

indicators on meter panel assembly 2A15A2 are

from 70 MHz intermediate frequency amplifier 2A5

controlled by Schmitt trigger circuits in alarm monitor

along with a predetermined reference signal level. The

2A12. Each Schmitt trigger circuit causes as associated

two signals are applied to differential amplifier Q3 and

indicator to light green (normal indication) or red (alarm

Q4. The carrier (if) monitor signal is derived from the

indication). The input signals to the alarm monitor

agc signal developed in 2A5 (para 2-22 (2)). As the 70

control the operation of an associated Schmitt trigger

MHz if input level to 2A5 increases, the age signal

circuit.

decreases; consequently, the carrier (if) monitor input to

the alarm monitor decreases. With the carrier (if)

(1) The traffic monitor signal is received from

monitor input at a lower level than the reference input to

af-rf amplifier 2A11 and is applied to operational

differential amplifier Q3 and Q4, the output of Q4 is

amplifier (integrated circuit) AR1 through an attenuator

high. The high output is applied through potentiometer

circuit. The operational amplifier output is detected by

R35 to Schmitt trigger Q17 and Q18. Potentiometer

detector CR1 and CR2 and applied as a traffic meter

R35 is used to set the input level to Schmitt trigger Q17

signal to the TRAFFIC position of the meter selector

and Q18. The high output from differential amplifier Q3

switch on 2A15A2 through potentiometer R8. The same

and Q4 causes Q17 to turn on, which in turn causes

output is also applied to Schmitt trigger circuit Q5 and

Q18 to turn off and Q19 to turn on. With Q19 turned on,

Q6 through emitter follower Q1. If the traffic monitor

the CARR IF indicator on meter panel assembly 2A15A2

signal exceeds a predetermined level, the dc voltage

lights green (normal indication). If the carrier (if)

developed by detector CR1 and CR2 will cause Q5 to

monitor signal input to differential amplifier Q3 and Q4

turn on causing Q6 to turn off and Q7 to turn on. With

is at a higher level than the predetermined reference

Q7 turned on, a low impedance path to ground is

input, Q17 turns off, Q18 turns on, and Q19 turns off

provided for the traffic normal indicator lamp, and the

causing the CARR IF indicator to change from green to

TRAF indicator lights green. Since Q6 is turned off, a

red. The red

high impedance path to ground is provided for the traffic

alarm indicator lamp (red) causing it to remain off.

When the input traffic monitor signal falls below the

Change 6

2-51