Functional Failure

TM 11-5820-695-35

inverter A5F, so A3D has a high at pin 13 and A8A has

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

a high at pin 13.

operation is as follows:

(4) Functional Failure. When a functional

(a) Both inputs to A3C are high and its

failure occurs, the output of at least one inverter (A5A,

output is low. Lamp driver Q1 is turned off and signal

AB, A5C, or A3B) switches to low and the output of A4 is

1RFFL is logic one. The low output of A3C is inverted

then high. The output of A4 is also high without a

to low by A5E and lamp driver Q2 is turned on. Signal

functional failure if the CABLE LOOP TEST switch is

ORFFL is logic zero. The RADIO TO CABLE MODEM

placed in TEST position. In either case, A3C has a high

indicator is lighted red.

at pin 8. The high from A4 is inverted by A5F, so A3D

(b) The inputs to A3D are high at pin 12

has a low at pin 13 and A8A has a low at pin 13.

and low at pin 13. The output, therefore, is high. Lamp

(5) Radio Traffic Normal-No Functional

driver Q3 is turned on and signal ORTFL is logic zero.

Failure. When radio traffic is normal and there is no

The high output from A3D is inverted by A5D and lamp

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

driver Q4 is turned off. Signal 1RTFL is logic one. The

exist and operation is as follows:

traffic out indicator is lighted red.

(a) A3C has a high at pin 9 and a low at

pin 8 and its output is high. Lamp driver Q1 is turned on

from A5F, when a radio-to-cable functional failure

and signal 1RFFL is logic zero. The high output of A3C

exists, or low at pins 2 and 3, from A7D, when a cable

is inverted to low by A5E, and lamp driver Q2 is turned

to-radio functional failure exists (para 2-5f(6)). The

off. Signal ORFFL is logic one and the RADIO TO

output of A8A is high and this is inverted to low by A9E.

CABLE MODEM indicator is lighted green.

Transistor Q5 is turned off, transistor Q6 is turned on,

and signal OMARY is low (alarm condition).

(b) A3D has a high at both inputs and

its output is low. Lamp driver Q3 is turned off and signal

(7) Radio Traffic Failure.

When a radio

ORTFL is logic one. The low output from A3D is

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

inverted by A5D and lamp driver Q4 is turned off.

functional failure signals are also affected and switch to

Signal IRTFL is logic zero and the traffic out indicator is

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

lighted green.

then exist and the relay driver circuit is activated as

explained in (2) above. Other operation is as follows:

1. If there is no failure in the cable-to-radio circuits, the

(a) The input signals to A3C are low at

output of NAND gate A2D is high (para 2-5f(5)) so A8A

pin 9 and high at pin 8 and its output is nigh. Otherwise,

has a high at pins 2 and 3. With all inputs high, the

operating conditions are as explained in (5)(a) above.

output of A8A is low and this is inverted to high by A9E.

(b) Both inputs to A30 are low and its

Transistor Q5 is turned on, Q6 is turned off and signal

output is nigh. Otherwise, operating conditions are as

OMARY is high (no alarm) .

explained in (6)(b) above.

(6) Radio Traffic Normal Functional Failure.

When radio traffic is normal and there is a functional

its output is high. Otherwise, operation is as explained

in (6)(c) above.

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