| All Alarm Systems must have at
least one detector. Most
detectors are normally closed
(NC) devices i.e they allow
the electric current to pass
through them when in a
non-alarm state. In alarm
state the detectors go Open
Circuit. This is detected by
the control panel and causes
an alarm to be signalled.
Several NO devices can be
daisy chained together such
that any device going open
circuit will cause an alarm.
Some detectors (e.g. pressure
mats) are Normall Open (NO)
devices and go Closed Circuit
in alarm state. These are
wired into the panel
differently than NO devices. |
