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A passive infrared sensor (PIR sensor) is an electronic sensor that measures infrared (IR) light radiating from objects in its field of view. They are most often used in PIR-based motion detectors . PIR sensors are commonly used in security alarms and automatic lighting applications.
A motion detector attached to an outdoor, automatic light. A motion detector is an electrical device that utilizes a sensor to detect nearby motion (motion detection).Such a device is often integrated as a component of a system that automatically performs a task or alerts a user of motion in an area.
Motion sensors create zones which cannot be accessed without sounding an alarm. Most cameras do now have a motion detection function, with some brands having thermal detection so they only activate when sensing a heat signature. This function is used so cameras do not pick up false alarms from trees blowing in the wind. [11]
The technology typically found in motion sensors to trigger an alarm includes infrared, ultrasonic, vibration and contact. Dual technology sensors combine two or more forms of detection in order to reduce false alarms as each method has its advantages and disadvantages. Traditionally motion sensors are an integral part of a home security system.
The word alarm comes from the Old French a l'arme meaning "to the arms", or "to the weapons", telling armed men to pick up their weapons and get ready for action because an enemy may have suddenly appeared. [1] The word alarum is an archaic form of alarm. It was sometimes used as a call to arms in the stage directions of Elizabethan dramas. [2]
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