Window Acoustic and Vibration Detectors
As you learned earlier, window sensors are used to detect the sound of breaking glass. Large glass doors such as patio doors are usually protected by mag-
netic switches. Windows in the home can also be protected by magnetic
switches if they can be opened; however, glass break detectors are recommended by most home security contractors to protect against an intruder
entering through a broken window.
Glass break detectors are available in either vibration type or acoustical type.
The vibration type is mounted on the glass or on a nearby wall.
Security system magnetic switches are designed for both normally closed (NC) and
normally open (NO) options.
An NC switch opens when the magnet is moved near
the switch, and an NO switch closes when the magnet is moved in close proximity
to the switch. This enables magnetic sensor-type switches to be used with various
types of security system designs.
Sensor door switches wired in parallel use NO contacts so that any closure of the contacts in the circuit activate an alarm condition.
Series circuits use NC magnetic switches where any opening of a switch results in
an open condition for the circuit, which triggers an alarm condition by the controller.
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