CHAPTER 5 FUNCTIONING OF ALARM EQUIPMENT

TM 11-5895-878-14&P

CHAPTER 5

FUNCTIONING OF ALARM EQUIPMENT

audible alarm is not enabled during the test.

5-1. Scope

This chapter describes the major/minor alarm panel, the

e. Panel Circuit Breaker. The panel circuit breaker

universal alarm panel, CAU/CCU alarm panel, and the

is located on the left side of the assembly with the reset

audible alarm panel. This chapter is made available to

button appearing on the front panel. Power is brought

aid in the operation and repair of the equipment. The

into the panel through connector pins 97 through 100.

equipment is LBAD fabricated; therefore, no

The breaker, if tripped, will give a ground-out alarm

manufacturer's literature is available. The alarm system

through pin 92.

is discussed in paragraph 2-19. Parts location and

identification for the assemblies discussed are given in

5-3. Universal Alarm Panel, Functional Description

appendix D.

The universal alarm panel is designed to connect two

redundant power supplies in parallel while providing the

5-2. Major/Minor Alarm Panel, Functional

necessary isolation between power supplies. The unit

Description

also senses the loss of power from one or both power

(fig. 4-1)

supplies and gives an alarm indication. The schematic

a. Major Alarm Circuit. A remote contact gives a

of the panel is shown in figure 5-2. The redundant

major alarm by presenting a ground at one of the odd

power supplies are isolated from one another by CR1

numbered pins on the panel connector (odd pins for

and CR2. if voltage is lost from PS # 1, the power

major alarms and even pins for minor alarms). This

supply side of diode CR1 goes to ground potential, relay

places a ground, through the diode, on terminal 1 of one

K1 goes to a de-energized state, and an alarm indication

of the Tellites. Since -48 VDC is supplied to Pin 2, the

is given through TB1, pin 3 or 4. If voltage is lost from

red Tellite lights. The ground is also extended to the

PS # 1, CR2 and K2 operate similarly to CR1 and K1.

COM1 terminal of the same Tellite. The relay contacts

in the Tellite are normally closed; therefore, this ground

5-4. CAU/CCU Alarm Panel, Functional Description

appears at the NC1 pin of the Tellite and pin 91 of the

(fig. 4-3)

panel connector. The ground on pin 91 causes an

a. The CAU/CCU Alarm Panel provides a common

audible alarm at the audible alarm panel (para 5-5).

alarm signal (ground) for as many as 20 Crypto Ancillary

b. Minor Alarm Circuit. In a similar fashion, a

Units and 20 Common Control Units. A separate alarm

remote contact gives a minor alarm by presenting a

connection is provided for each type of equipment.

ground at one of the even numbered pins on the panel

b. The panel is powered by 120 vac, which is

connector. The operation is the same as a major alarm

connected through terminals 3 and 4 of TB2 to a 6 vdc

except the amber light is lit by placing the ground on pin

power supply. The + and -6 volt output of the power

3 of the Tellite.

supply is used to power two transistor circuits (Q1 and

c. Acknowledge Circuit. The alarm, whether major

Q2) and operate two relays (K1 and K2).

or minor, is acknowledged by pressing the Tellite. This

c. Up to 20 CCU alarm outputs may be connected

action manually operates the relay contact thus

to TB3. Each input is isolated from other equipment

removing the ground from NC1 and puts it on the NO1

alarm circuits by diodes CR1 through CR20. When 0

of the Tellite. This removes the ground from Pin 91;

vdc is applied to all inputs (on TB3) transistor Q1 is held

therefore, the audible alarm is silenced. Due to the

cut off. When + 6 vdc is applied through an isolation

jumper from NO1 to Pin 4, the ground is placed on a

diode to the base of Q1, the transistor conducts current

locking coil within the Tellite. Since -48 VDC is wired to

through the coil of relay K1, closes its contacts, placing

pin 5, this coil is energized, locking the Tellite relay in its

ground on the panels CCU alarm output (terminal 5 of

present state, once the Tellite is no longer depressed.

TB2).

Once the fault is cleared and the ground is removed

d. The panel also provides connections for up to

from the Tellite, the light goes out and the relay unlocks.

20 CAU alarm inputs. Due to the difference in the alarm

d. Test Buttons. All major alarms may be tested

logic, the isolation diodes are connected in the opposite

by depressing the red button on the front of the alarm

direction as they are for CCU operation. The circuit

panel. The minor alarms may be tested by depressing

operates similarly to the CCU circuit, except for the

the black button. These buttons place a ground on the

following: (1) The transistor (Q2) is a PNP in place of a

appropriate pins on all the Tellites, thus causing the

NPN; (2) An alarm from a CAU is +6 vdc; (3) Relay K2

lights to energize. The diodes located between the

contacts provide ground at the CAU panel alarm output

Tellites and the connector prevent the ground from

(terminal 1 of TB2).

being placed on COM1 and Pin 91; therefore, the

5-1