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Smoke detector mounted on a ceiling. A smoke detector is a device that senses smoke, typically as an indicator of fire.Smoke detectors/alarms are usually housed in plastic enclosures, typically shaped like a disk about 125 millimetres (5 in) in diameter and 25 millimetres (1 in) thick, but shape and size vary.
Conceptual through-beam system to detect unauthorized access to a secure door. If the beam is interrupted, the detector triggers an alarm. A photoelectric sensor is a device used to determine the distance, absence, or presence of an object by using a light transmitter, often infrared, and a photoelectric receiver. They are largely used in ...
Fire alarm systems are required in most commercial buildings. They may include smoke detectors, heat detectors, and manual fire alarm activation devices (pull stations). All components of a fire alarm system are connected to a fire alarm control panel. Fire alarm control panels are usually found in an electrical or panel room.
The alarm transmission methods covered under UL 365 can be categorized under standard line security or encrypted line security. The systems are required to operate within the limits of Class 2 remote control and signal circuits as defined by the National Electrical Code, NFPA 70. [15]
A microbolometer is a specific type of bolometer used as a detector in a thermal camera. Cryogenic detectors are sufficiently sensitive to measure the energy of single x-ray, visible and infrared photons. [18] Pyroelectric detectors detect photons through the heat they generate and the subsequent voltage generated in pyroelectric materials.
Normally, light from the light source shoots straight across and misses the sensor. When smoke enters the chamber, it scatters the light, which then hits the sensor and triggers the alarm. Photoelectric smoke detectors typically respond faster to a fire in its early, smoldering stage, before the source of the fire bursts into flames.