Zone Latching; Zone Latching Sequence - Mircom Flex-Net Phase II Application Manual

10.0

Zone Latching

Zone latching is a useful technique that can be applied to latch normally non-latching zones
such as monitor, trouble, and non-latching supervisory zones. Latching zones can be used to
maintain outputs or timers even if the original input is no longer active.
An example of when a latching zone is used would be to add a strobe delay for a period of
time after a page has occurred. The input being the page active status would initially activate a
zone. This zone is correlated to the output strobes that would activate with the activation of the
zone. However, the zone would need to remain active once the page active status is
deactivated therefore latching the zone is required. A timer can also be used to unlatch the
zone upon expiring.

10.1 Zone Latching Sequence

The basic sequence involves an initiating device, status, or zone and the zone used to latch
itself. The "latching zone" must have multiple methods of becoming active, either by the
activation of the initiating device/status/zone or by the "latching zone" itself. This is done
through advanced logic. Refer to the example below.
The equation shown is specified in the advanced logic tab of the latching zone, 01-00-**-IZ-
011
01-00-00-IN-007 – Initiating device
01-00-**-IZ-011 – Latching Zone
Note: the latching zone is referenced in the advanced logic equation for the latching zone. This
allows the zone to latch itself.
Once the initiating device becomes active, the latching zone will become active as the
advanced logic equation would be satisfied. If the initiating device becomes de-active or is
restored, the latching zone will remain active as the equation would still be satisfied. Thus the
zone is latched. A system reset would be required to unlatch the zone similar to a normally
latching zone such as alarm.
By modifying the advanced logic equation with a timer, the latch can be set to unlatch upon the
expiration of the timer. For example,
01-00-00-IN-007 OR (01-00-**-IZ-011 AND NOT **-**-**-TM-021 EQU TIMER_EXPIRED)
The equation would remain satisfied as long as timer 21 does not expire. Upon expiration of
timer 21, and the initiating device is restored, the equation will no longer be satisfied and the
latching zone would be restored.
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01-00-00-IN-007 OR 01-00-**-IZ-011
Zone Latching