Alarm Monitor 1A12A15, Asynchronous Mode

TM 11-5820-695-35

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

summary alarm output signal for cable-to-radio circuits

circuits. The summarized alarm signals activate green

(para 2-6h).

and red status indicators, a major alarm relay, and

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

circuits of alarm monitor 1A12A6 control the CABLE-

driver Q10 is turned on and output signal 1CTFL is logic

TO-RADIO MODEM indicator on meter panel assembly

zero. The high from A3E is inverted to low by A3F,

1A16A4 and the shelter mounted traffic in indicator.

lamp driver Q11 is turned off and output signal OCTFL

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

is logic one. The traffic in indicator is lighted green.

circuits functional alarm signals from 1A12A13

(1CRFAIL), 1A12A14 (1CCFAIL), and 1A12A4

(6) Cable

Traffic

Normal-Functional

(1CRLFAIL), and the cable traffic signal (XCPCM) from

Failure. When cable traffic is normal and there is a

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

functional failure, the conditions of (1) and (4) above

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

exist and operation is as follows:

the pcm signal is processed in sequence in 1A12A13,

1A12A14 and 1A12A4, a functional failure in 1A12A14

(a) The inputs to A4C, from both A

causes both 1CCFAIL and 1CRLFAIL signals to switch

B and A3E, are high and the output is low Lamp driver

to logic one, and a functional failure in 1A12A13 causes

Q9 is turned off and output signal 1CFFL is logic one.

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

The output of A4C, inverted to high by A3C, turns on

failure of the cable traffic signal, all three functional

lamp driver Q8 and output signal OCFFL is logic zero.

failure signals switch to logic one because each circuit

The CABLE TO RADIO MODEM indicator is lighted red

(1A12A13, 1A12A14 and 1A12A4) then loses the pcm

signal. Alarm monitor 1A12A15 uses these four inputs

(b) Negative OR gate A2A receives

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

a low from A4C and its output is high ((5)(b) above).

failure has occurred--functional failure or cable traffic

The high from A2A is inverted to low by A2B and

failure.

applied to A1A (para 2-6h).

(1) Cable Traffic Normal. When cable

traffic (XCPCM) is being detected, and signal OPSALM

Q10, Q11, 1CTFL and OCTFL are as explained in (5)(

is normal (high), both inputs to NOR gate A7A are high

c) above The traffic in indicator is still lighted green.

and its output is low. The output of inverter A6A is then

logic zero (high) and lamp driver Q10 is turned on. The

(7) Cable Traffic Failure. When a cable

logic zero from A6A is inverted by A6B and lamp driver

traffic failure occurs (loss of the XCPCM signal), all

Q11 is turned off. Output OCTFL is logic one, 1CTFL is

functional failure signals are also affected and change to

logic zero and the traffic in indicator is lighted green.

logic one (high). The conditions of (2) and (4) above

then exist and operation is as follows:

(2) Cable Traffic Failure When loss of the

cable traffic signal (XCPCM) occurs, or signal OPSALM

(a) The inputs to A4C are high from

is logic 0, the output of inverter A6A is low and lamp

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

driver Q10 is turned off. The low from A6A is inverted

operation is as explained in (5)(a) above.

by A6B and lamp driver Q11 is turned on. Output

OCTFL is logic zero, 1CTFL is logic one and the traffic

(b) Negative OR gate A2A receives

in indicator is lighted red.

a low from A3E and its output is high. The high output

from A2A is inverted to low by A2B and applied to A1A

(3) No Functional Failure. The 1CRFAIL,

(para 2-6h).

1CCFAIL and 1CRLFAIL signals are inverted by

inverters A9B, A9A and A9C, and the resulting output

signals are applied to NOR gate A8B. Signal OPSALM

driver Q10 is turned off and output signal 1CTFL is logic

is inverted successively by inverters A9F and A9D The

one. The low from A3E is inverted to high by A3F; lamp

output of A9D is connected to NOR gates A7A and A8B

driver Q11 is turned on and output signal OCTFL is logic

When there is no functional failure, input signals

zero. The traffic in indicator is lighted red.

1CRFAIL, 1CCFAIL and 1CRLFAIL are low (logic zero)

and OPSALM is high (logic zero) and all inputs to A8B

Alarm Monitor 1A12A15, Asynchronous

are high. A8B then applies a low (logic zero) to NAND

Mode (fig. 5-7.1 and 5-33.1). Alarm monitor 1A12A15

gate A7B.

receives alarm signals from other circuits of digital data

modem 1A12 and uses logic combinations of these

alarm signals to generate traffic and functional alarm

Change 2 2-16