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signal relay operating and closing its set of contacts.
Figure 9-17 is a schematic of an alarm switchboard.
The alarm switchboard is an electrical system
installed on board ship for the detection and warning
Test Operation
of a variety of important functions or conditions that
require continuous monitoring. It also gives warning
The supervisory alarm system is designed to
when trouble or failure occurs in the alarm circuit and
require very little attention. Almost any trouble that
indicates which section of the equipment is involved.
may affect the system will give both an audible and a
Alarm switchboards are normally used to monitor
visual signal in the form of an alarm, or trouble alarm.
alarm, safety, and warning systems that have sensors
However, the system is arranged so that periodic tests
located in a large number of spaces. The type IC/SM
of all circuits may be made easily and quickly from
alarm switchboard is the latest type of switchboard
the alarm switchboard. These procedures test only the
installed on board ships today and is the only one we
panel and line units. External wiring must be checked
will discuss in this training manual.
at the panel for insulation resistance and continuity.
The type IC/SM alarm switchboard uses
The silent test switch is centrally located at the top
individual line display alarm modules to present
of the alarm switchboard. Keep this switch in the
multiple steady and flashing visual displays together
N O R M A L position except when testing the
with multiple audible signals to indicate the state of
switchboard circuits. For the silent alarm test, place
the sensors associated with each individual line.
the silent test switch in the SILENT ALARM TEST
position. This disconnects the extension signal relay,
The type IC/SM alarm switchboard is available in
that in turn controls the alarm bell and connects the
many different sizes. Figure 9-18 is an illustration of
ALARM TEST light into the circuit in place of the
an IC/SM-50 alarm switchboard. This switchboard is
bell. When the silent test switch is placed in either test
capable of monitoring 50 individual lines. Each
position, the TEST LIGHT on the panel will flash.
switchboard contains a common alarm section and a
line display section. The common alarm section
To test the capacity of each circuit to act as an
includes all components located on the control panel,
alarm, place the silent test switch in the SILENT
as well as the subassemblies common to any size alarm
ALARM TEST position. Place the circuit test switch
switchboard. The line display section contains the
on the line unit in the TEST position. The ALARM
individual display modules, one for each circuit.
TEST lamp will light and the target will show red on
the circuit being tested, If the circuit is in proper
Common Alarm Section
condition to turn off the ALARM TEST light, return
the station to NORMAL.
The upper section of the switchboard is the
To perform the silent trouble test, place the silent
common alarm section. The primary function of the
test switch in the SILENT TROUBLE TEST position.
common alarm section is to interpret commands from
Placing the switch in this position disconnects the
the line display alarm modules and, in turn, generate
trouble buzzer and places the silent test lamp in the
the appropriate audible signals. The audible signals
circuit. As in the silent alarm test, the test lamp will
produced are a wailing (or siren) tone, a pulsating
also flash, Each supervisory circuit is tested by
tone, and a steady tone. Each of these signals
moving the line unit test switch slowly from
represents a particular system condition. An alarm
NORMAL to OFF. The yellow target will show on the
condition activates the wailing tone, the supervisory
line unit directly above the line unit test switch, and
failure activates the steady tone, and a power failure
the TROUBLE TEST lamp on the alarm panel will
activates the pulsating tone.
flash momentarily. The yellow target will show as
long as the line unit test switch is in the OFF position.
The secondary function of the common alarm
The TROUBLE TEST lamp will darken as soon as the
section is to detect and indicate grounds in the
line unit test switch is fully operated. If the yellow
switchboard itself or in any of the individual line
target does not show, the circuit is inoperative and
should be repaired.
Mounted on the front of the common alarm section
Upon completion of the silent alarm test and the
are two ground detection indicators, a visual-audible
silent trouble test, take care to see that all test switches
switch, an alarm silence indicator, a dimmer control,
are returned to normal.
a speaker, and a fuse holder. Located inside the

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