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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
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
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
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

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