-24VDC, through resistor R2, terminal 4, out the
building wiring to one side of the alarm initiating
devices, and back to terminal 3, through the EOL
resistor, out the building wiring to the other side of
the alarm initiating devices, and back to terminal 1.
From terminal 1, current flows through zone
trouble relay K2 (energizing K2) and through
alarm relay K3. Because of the current limiting
effects of the EOL resistor, relay K2 is energized
and relay K3 is de-energized.
Trouble Condition
If an open occurs in the alarm circuit, zone trou-
ble relay K2 de-energizes and its contacts transfer.
Current from terminal -24VDC flows through con-
tacts K2A (l&3) and splits into two paths.
One path is through terminal 6, the ZONE
TROUBLE lamp (illuminating the lamp), to termi-
nal +24. The other path is through diode D4 to
terminal 5.
From terminal 5, current flows through diode
DlO to relay Kl. With a negative potential on both
sides of relay Kl it de-energizes and its contacts
transfer.
NOTE: Relay Kl is very voltage sensitive and
consequently diode DlO is used to equalize the
voltage that is dropped across blocking diode
D9. This insures that exactly the same voltage
is
on both sides of relay K 1.
When relay Kl de-energizes, supervisory power
(12OVAC) is applied from terminal SP, through
contacts KlA (l&4), terminal EL2, to the NOR-
MAL/SILENCE switch NORMAL position where
the current flow splits into two paths.
One path is through the OP. POWER TROUBLE
lamp (illuminating the lamp)
to
terminal NEUT.
The other path is through resistor R4 and the
rectifier (which causes the Sonalert to sound) to
terminal NEUT. Resistor R4 is used to drop the
line voltage to the operating range of the Sonalert
(6 to 28VDC).
The’ Sonalert can be silenced by placing the
NORMAL/SILENCE switch in the SILENCE posi-
tion. When this switch is in the SILENCE position,
the current path to the rectifier is broken and the
Sonalert is silenced.
Trouble Repaired
When the trouble is repaired, relay Kl energizes
and its contacts transfer. When the Kl A contacts
transfer, the circuit from terminal SP through the
OP. POWER TROUBLE lamp is broken and the
OP. POWER TROUBLE lamp goes out.
Simultaneously, 120VAC from terminal SP flows
through the transferred contacts K IA (l&3), the
NORMAL/SILENCE switch SILENCE position, re-
sistor R4 and the rectifier which causes the Sonalert
to sound (“ring-back”). The “ring-back” feature
insures that the NORMAL/SILENCE switch will be
in the NORMAL position during normal operation.
The Sonalert can be silenced by placing the
switch in the NORMAL position.
Alarm Condition
When the alarm initiating device contacts are
closed, the EOL resistor is bypassed and the in-
creased voltage across alarm relay K3 causes K3 to
energize (zone trouble relay K2 is unaffected and
remains energized). When alarm relay K3 energizes,
its contacts transfer and current from terminal
-24VDC flows through contacts K3A (l&3) where
it splits into three paths.
The first path is through diode D3, terminal 8,
the ZONE ALARM lamp (illuminating the lamp) to
terminal +24.
The second path is through diode D2, terminal 7
to the signal panels which causes the alarm signal-
ing devices to operate.
The third path is through diode D 1, terminal 1,
relays K2 and K3 to terminal +24 to provide a
holding circuit for relay K3.
NOTE: Diode Dl is removed for coded opera-
tion and relay K3 does not latch.
Reset Circuit
The KEY RESET switch is used to silence the
alarm signaling devices and to return the system to
normal operation after an alarm. When the KEY
12
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