AF Amplifier 1A12A6 - TM-11-5820-695-350059

TM 11-5820-695-35

to the cable system through the radio-to-cable circuits

(2) Cable Traffic Failure. When loss of

(para 2-6e).

the cable traffic signal (XCPCM) occurs, the output of

AF Amplifier 1A12A6 (fig. 5-7 and 5-34).

inverter A3E is low and lamp driver Q10 is turned off.

The low from A3E is inverted by A3F and lamp driver

Q11 is turned on. Output OCTFL is logic zero, 1CTFL is

The cable-to-radio circuits of af amplifier 1A12A6

logic one and the traffic in indicator is lighted red.

amplify the orderwire signal. The cable-to-radio circuits

of 1A12A6 are comprised of an input amplifier, a low

(3) No Functional Failure. The 1CRFAIL,

pass filter with cutoff frequency of 2000 Hz, and a power

amplifier. The amplified output cable receive orderwire

1CCFAIL and 1CRLFAIL signals are inverted by

(CCROW) of 1A12A6 is applied to the "thru ow rec"

inverters A7B, A7C and A7F, and the resulting output

input of orderwire assembly 1A13. A level detector

signals are applied to negative OR gate A1B. When

circuit at the output generates a dc voltage when the

there is no functional failure, these signals are all low

orderwire signal is active. The dc voltage is available at

(logic zero) and all inputs to A1B are high. A1B then

a test point for monitoring and testing purposes.

applies a low (logic zero) to NAND gate A4C.

Alarm Monitor Synchronous Mode 1A12A

(4) Functional Failure. If any functional

(fig. 5-7 and 5-33). Alarm monitor 1A12A5 receives

failure exists, A1B has at least one input which is low. If

alarm signals from other circuits of digital data modem

a cable traffic failure occurs, all inputs to A1B are low.

1A12 and uses logic combinations of these alarm

In either case, A1B applies a high (logic one) to A4C.

signals to generate traffic and functional alarm

indications for the radio-to-cable and cable-to radio

(5) Cable Traffic Normal-No Functional

circuits The summarized alarm signals activate green

Failure. When cable traffic is normal and there is no

and red status indicators, a major alarm relay, and

functional failure, the conditions of (1) and (3) above

control a bypass orderwire relay. The cable-to-radio

exist and operation is as follows:

circuits of alarm monitor 1A12A5 control the CABLE-

TO-RADIO MODEM indicator on meter panel assembly

(a) The inputs to A4C are low from

1A16A4 and the shelter mounted traffic in indicator.

A1B and high from A3E. The output of A4C is then

Two kinds of signals are monitored by the cable-to-radio

high, and as a result, lamp driver Q9 is turned on and

circuits-functional

alarm

signals

from

1A12A2

output signal 1CFFL is logic zero. The output of A4C,

(1CRFAIL),

1A12A3

(1CCFAIL,)

and

1A12A4

inverted to a low by A3C, turns off lamp driver Q8 and

(1CRFAIL); and the cable traffic signal (XCPCM) from

output signal OCFFL is logic one. The CABLE TO

1A12A2. When a functional failure occurs in 1A12A4,

RADIO MODEM indicator is lighted green.

alarm signal 1CRLFAIL, is activated (logic one). Since

the pcm signal is processed in sequence in 1A12A2,

(b) The output of negative OR gate

1A12A3 and 1A12A4, a functional failure in 1A12A3

A2A is applied to NAND gate A2B The logic action at

causes both 1CCFAIL and 1CRLFAIL signals to switch

A2B depends on the operating mode in use. When

to logic one, and a functional failure In 1A12A2 causes

Radio Set AN/GRC-144 is being used in radio repeater

all three signals to switch to logic one. Also, if there is a

mode, the cable-to-radio circuits of digital data modem

failure of the cable traffic signal, all three functional

1A12 are not used and signal ORRM is logic zero. The

failure signals switch to logic one because each circuit

output of A2B is then always high because it is inhibited

(1A12A2, 1A12A3 and 1A12A4) then loses the pcm

by the logic zero (ORRM) at pin 5. This prevents

signal. Alarm monitor 1A12A5 uses these four inputs to

erroneous application of a cable-to-radio fault indication

the cable-to-radio circuits to distinguish which kind of

to negative OR gate A1A when in radio repeater mode.

failure has occurred, functional failure or cable traffic

When Radio Set AN/GRC-144 is being used In the

failure.

cable terminal mode, signal ORRM is logic one. NAND

gate A2B then has logic one at pin 5 and it acts as an

(1) Cable Traffic Normal. When cable

inverter for the -signal at pin 6. When a functional

traffic (XCPCM) is being detected, the output of inverter

failure occurs, negative OR gate A2A has high inputs

A3E is logic zero (high) and lamp driver Q10 is turned

from A4C and A3E and it applies a logic zero (low) to

on. The logic zero from A3E is inverted by A3F and

A2B. The low is inverted to high by A2B, and applied to

lamp driver Q11 is .turned off. Output OCTFL is logic

negative OR gate A1A This is the

one, 1CTFL is logic zero and the traffic in indicator is

lighted green.

Change 1 2-15