Do Alarm Systems Require Normally Open Or Normally Closed Sensors
Alarm systems are designed to use 'open loop' burglary sensors. While they are called 'open loop', they are actually 'normally closed' when the magnet is near the sensor or in other words the zone is 'safe.
Motion, glass break and other burglary sensors are also 'normally closed' when safe.
Smoke and water sensors are usually 'normally open' and are used with an EOL resistor.
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