Alarm Panels and Alarm Switcboards

the audible signal. When the audible signal sounds, the

ALARM PANELS

lamps illuminate the colored glass and brass target of

The alarm panel consists of a 3-inch alarm bell, a

the indicator and identify the alarm being sounded.

low-pitch trouble alarm buzzer, a three-position test

Standard watertight lamp indicators are also

switch, a test light, an alarm test light, a trouble test

designed as two-dial variable-brilliancy, two-dial

light a pilot light, negative and positive ground lamps,

fixed-brilliancy, and four-dial variable-brilliancy

and four double-fuse holders (fig. 9-13).

units. Two 6-volt lamps are connected in parallel and

The alarm bell, type IC/B1S4, is mounted in the

mounted behind each dial. A colored jewel disk and

upper left-hand comer of the alarm panel. The alarm

sheet-brass target are illuminated from the rear by the

bell sounds whenever an alarm condition exists,

two lamps.

The trouble buzzer, type IC/21S4, is mounted in the

Special lamp indicator panels are designed to give

upper right-hand comer of the alarm panel. It is ener-

good visibility at all viewing angles. These panels

gized when there is a malfunction in the alarm circuit.

contain rows of prism-shaped red and green jewels,

The test switch, type SR03, is a three-position,

Each indicator has two 6-volt lamps in parallel.

four-pole rotary switch, It is located in the center of the

alarm panel. One section of the switch is not normally

used, and can be used as a spare if another section

ALARM PANELS AND ALARM

malfunctions. The middle switch position is NORMAL,

SWITCHBOARDS

the left position is SILENT ALARM TEST, and the

right position is SILENT TROUBLE TEST.

Alarm panels and alarm switchboards are

normally installed in spaces that are continuously

A TEST LIGHT is mounted between the bell and

manned both underway and in port. Alarm panels and

the buzzer. It is energized anytime the test switch is in

alarm switchboards are capable of monitoring a

any position other than NORMAL. When the TEST

LIGHT is energized, it indicates the alarm bell or

number of circuits, depending on the type and size of

trouble buzzer have been disconnected from its circuit.

the panel or switchboard used. All systems using

alarm panels or alarm switchboards have a

ALARM TEST and TROUBLE TEST lamps are

supervisory feature that indicates whether the system

mounted on the left and right of the test switch, respec-

is operating in a normal mode. This supervisory

tively, The ALARM TEST light takes the place of the

feature usually consists of a 7000-ohm, 5-watt resistor

bell in the circuit when the test switch is put in the

connected across the terminals of the sensing device

SILENT ALARM TEST position. The TROUBLE

TEST light takes the place of the buzzer when the test

used in each system. When two or more sensing

switch is placed in the SILENT TROUBLE TEST po-

devices are used in the same line, the supervisory

sition.

resistor will be connected across the terminals of the

last sensing device in the line. The primary power

A PILOT LIGHT is located underneath the test

source for alarm panels and alarm switchboards is

switch. It is energized whenever power is available to

120-volt, 60-Hz ships' service power.

the alarm switchboard.

Ground indicating lamps are located on either side

There are three basic conditions for each system

of the PILOT LIGHT. The GROUND NEG LINE lamp

being monitored. The first condition is the supervisory

is on the left and the GROUND POS LINE lamp is on

or normal condition. This condition exists when the

the right side of the panel.

system is functioning correctly. During this condition,

There are four double-fuse holders across the bot-

a small continuous current flows in the circuit, which

tom of the alarm panel. These fuses are for remote

indicates that the circuit is in a normal condition.

alarms.

The second condition is the alarm condition. This

The most common types of alarm panels used with

condition exists when there is an increase in current

the alarm, safety, and warning systems are the B-51 and

flow in the circuit.

the B-52. The B-51 is a two-line panel, and the B-52 is

The third condition is the trouble condition. This

a four-line panel. The only difference between these two

condition exists when an open in the circuit stops the

panels is the number of lines. We will discuss the

flow of current in the circuit. Under this condition, an

operation of the B-51 alarm panel in the following

alarm condition cannot be detected.

paragraphs.

9-11