FIRE ALARM DIGITAL MONITOR I/O BOARD, CLASS A, 562-466
The Class A fire alarm digital
monitor I/O board
provides McCulloh
loop operation for monitor zones 1
through 4. Zones
6 through 8 can be used for
-2":
standard (Class B) operation. When one of zones 1
through 4 experiences an open, relays Kl and K2 on
the board energize to place Class A zones on the alternate (secondary) zone wiring. When this happens, zone
5 is used to report the McCulloh loop trouble. Since the board does not report specifically which Class A zone
is in trouble, you must use switch Sl to momentarily deenergize relays Kl and K2. The troubled zone will then
be reported. Here’s an example.
Suppose zone 3 on a Class A board opens. At the BMUX, you would see a trouble report for zone 5 on that board.
You would then proceed to the appropriate ET and locate the troubled I/O board. By activating switch Sl, you
momentarily deenergize the McCulloh loop relays long enough to allow the troubled zone to be reported (in this
case, a zone 3 trouble would be reported when you activated Sl).
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