RFL 9780 RFL Electronics Inc.
April 8, 2003 6-23 (973) 334-3100
6.5.1.14 ALARM OUTPUT CIRCUIT
The alarm output circuit will produce a LOGIC_ALM output at edge connector pin A20 whenever the
9780 Logic Module is not in an alarm state. This output is used to energize the alarm relay in the
(normal) no-alarm condition. If an alarm condition occurs, the transistor associated with the alarm
output circuit is turned off causing the alarm relay to dropout. ALARM LED (DS5) will also light to
indicate that the 9780 is in the alarm state. The LOGIC_ALM output will block the guard and trip
outputs when the alarm picks up and until the alarm drops out. The input to the unblock trip restore
timer will be blocked as well.
Once the alarm timer clears the alarm condition, the transistor will turn on again, and DS5 will go out.
The alarm relay will pull in again, which is the normal condition.
If an under-voltage condition is detected, the PWR_FAIL and/or POWERFAIL2 inputs to the 9780
Logic Module will be logic-low. Both signals in the logic-low state will generate a logic-low POWER
signal that will force an alarm condition for the combined period of the under-voltage condition, alarm
drop-out timer, and an additional 600 ms.
The status of the alarm output circuit is recorded by the sequence of events module.
6.5.1.15 UNBLOCK SECURITY TIMER
For the following discussion refer to Figure 6-4.
The unblock security timer is used to disable the unblock trip output for shorter losses of channel than
its preset time interval. The unblock security timer is only applicable for valid low signal conditions.
A VALID_LOW signal condition is applied to the unblock security timer once the following conditions
are satisfied:
1. A logic-high LO SIG input signal from the threshold detector is applied to AND1.
2. UNBLOCK_CHANNEL signal is logic-high indicating the unblock trip restore timer has
been satisfied by 50ms of Guard or non-low level condition. The SR Flip-Flop is SET by the
UNBLOCK signal, and its high output is applied to AND1.
3. A logic-low BLOCK_CHANNEL signal is applied to AND1 indicating a
LOW_SIGNAL_TRIP is not currently active, and did not occur within the last 5ms.
If a logic-high VALID_LOW signal exceeds the preset time interval of the unblock security timer, the
PASS_SECURITY signal will go to a logic-high. A logic-high PASS_SECURITY signal triggers the
unblock window timer.
6.5.1.16 UNBLOCK WINDOW TIMER
The unblock window timer is a non-retriggerable one shot which will hold the trip output for a preset
time interval once a logic-high PASS_SECURITY signal is applied to its input. The
LOW_SIGNAL_TRIP is ultimately applied to the trip output circuitry, energizing electro-mechanical
and solid-state relays. The LOW_SIGNAL_TRIP also RESETS the SR Flip-Flop, limiting the
operation to only one unblock trip output per channel disturbance.
If an abnormal condition causes the alarm to pickup, the LOW_SIGNAL_TRIP will be blocked until
the abnormal condition ceases and the alarm drops out.
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