the audible signal. When the audible signal sounds, the
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,
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,
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
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.
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.