Most
contacts are "normally closed and consist of two parts; a switch
which is mounted on the fixed structure (door or window frame) and a
magnet which is mounted on the door or window. When the magnet is in
close proximity to the switch, the magnetic field closes the switch.
Opening the door or window causes the switch to be opened, triggering
an alarm condition. In addition to magnetic contacts there are switches
that mount in the frame. The action of opening the door or window allows
the switch to pop out, opening the switch.
When
it is normal to leave a window partially open during the alarmed state,
the window can be configured with two magnets and one switch. In this
configuration, the first magnet is mounted for the window in the fully
closed position. The second magnet is mounted for alignment with the
switch when the window is in the partially opened position and will
trigger the alarm if the window is fully opened.
Contacts
should be installed on all doors and windows that are accessible, providing
early intrusion notification. Window coolers or other externally mounted
apparatus that can be easily removed may also require protection with
security contacts.
Commercial Security |
Residential
Security
