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 TM 55-1905-220-14-9
4-48. ALARM SWITCHBOARD - MAINTENANCE INSTRUCITONS (Continued).
terminal "2F" of the two line unit, back to terminal "2F" on the alarm switchboard; then to terminal "L2" to the
other side of the 120V A.C. source of supply.
(f) As the circuit test switch is moved to "Off" position, contacts 1 and 4 are opened, thus
darkening the "Trouble Test" lamp, PL3. Careful manipulation of the circuit test switch will cause the "Trouble
Test" lamp to glow steadily, otherwise it will glow only momentarily.
CAUTION
Silent Alarm Test Switch
Upon completion of the "Silent Alarm Test" and the "Silent Trouble Test" (or
either one if conducted without the other), care should be taken to see that all
test switches are returned to normal.
The silent alarm test switch, S, mounted in the top section of the Alarm
Switchboard, locks in both test positions and must be returned to normal
manually. A warning is provided by the "Test Light" PL1, which will flash
intermittently as long as the switch is in either test position. This warning is
provided because leaving this test switch in either test position will render one
or the other of the audible alarm signals useless.
e. Grounds.
(1) A multiple ground is the term used to indicate more than one ground on the same side of the
system; that is, more than one positive or more than one negative ground. Simultaneous grounds are those
that occur on opposite sides of the system at the same time.
(2)
Single or Multiple Grounds.
(a) Lighting of negative ground lights (full brilliance). This indicates a single or multiple ground on
FF1, FF2, FF3, etc.
(b) Lighting of positive ground lights (full brilliance). This indicates a single or multiple ground on
F1, F2, F3, etc.
4-1235
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