RFL 9780 RFL Electronics Inc.
April 8, 2003 6-22 (973) 334-3100
6.5.1.11 BLOCKING LOGIC CIRCUIT
The CE_HIGH, CE_LOW, LO SIG and HI SIG signals are applied to the blocking logic circuit where
the noise is further processed and evaluated. The logic-low BLOCK output signal will block the
TRIP_INPUT signal when any of these signals is active. However, the CE_HIGH and CE_LOW
signals will not block the trip channel if the TRIP_HELD signal is active indicating a valid trip. The
BLOCK signal is also applied to output pin BLK_OUT (C15) at the module edge connector; this drives
logic on the LM/SL Module.
6.5.1.12 30 MS PULSE STRETCHER
Noise disturbances are usually a series of short-duration pulses. Although they indicate an abnormal
condition, they may not be long enough to trigger the alarm timer. The pulse stretcher is used to
elongate these short pulses so that the alarm timer can respond to them. This pulse stretcher can be
triggered by a logic-low BLOCK signal generated by the threshold detectors or carrier envelope noise
detector. The pulse duration will be equal to the period of the disturbance plus the 30 ms period of the
pulse stretcher. For example, 1 ms noise disturbances occurring every 20 ms for 100 ms will generate a
130 ms pulse, triggering an alarm if the alarm pick-up timer were preset to 100ms. The logic-high
output pulse, NOISE_STRETCH, will trigger the alarm timer. A logic-high TRIP_HELD generated by
a valid trip, or logic-high applied to STOP_ALARM at edge connector pin C29 will prevent any
disturbances from triggering the pulse stretcher that may activate the alarm timer.
6.5.1.13 ALARM TIMER
The alarm timer is triggered by any abnormal condition detected by the receiver logic of the 9780 Logic
Module. The logic-high NOISE_STRETCH signal applied to the input signal of the alarm timer
indicates this condition. If the condition persists for the entire preset alarm pick-up time interval, the
alarm output circuit will be activated, indicating that the 9780 is in alarm mode. The LOGIC ALARM
indicator DS5 will be lit, the logic alarm relay will be de-energized, and the guard output and trip
output will be blocked.
In order to clear the alarm, the NOISE_STRETCH input must be low for a period exceeding the preset
alarm dropout time interval.
In the no-alarm state, the following conditions are present in the alarm timer:
1. The carrier envelope noise detector outputs (CE_HIGH and CE_LOW) are not active.
2. The threshold detector outputs (LO SIG and HI SIG) are not active.
3. Bipolar noise (BNOISE) is not active.
4. A valid trip or guard is being received.
5. The PWR_FAIL and POWERFAIL2 inputs (edge connector pins A17 and C16 ) received from
the power supply are not active. Both must be active simultaneously to be considered a critical
power fail condition. POWERFAIL2 is forced active when optional redundant supply is not
installed.
6. The LOGIC ALARM indicator DS5 is off.
7.The alarm output circuit is turned on, and the 9780 logic alarm relay is energized. Note that a
constant logic-high applied to the STOP_ALARM input at edge connector pin C29 can manually
turn off an active alarm. However, it will not turn off an active alarm triggered by a power failure
condition.
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