12-30VDC SMOKE DETECTOR RESETABLE 2WIRE

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Description

12-30VDC SMOKE DETECTOR RESETABLE 2WIRE

12-30VDC SMOKE DETECTOR RESETABLE 2WIRE

smoke detector is a device that senses smoke, typically as an indicator of fire. Commercial security devices issue a signal to a fire alarm control panel as part of a fire alarm system, while household smoke detectors, also known as smoke alarms, generally issue a local audible or visual alarm from the detector itself.

Smoke detectors are housed in plastic enclosures, typically shaped like a disk about 150 millimetres (6 in) in diameter and 25 millimetres (1 in) thick, but shape and size vary. Smoke can be detected either optically (photoelectric) or by physical process (ionization), detectors may use either, or both, methods. Sensitive alarms can be used to detect, and thus deter, smoking in areas where it is banned. Smoke detectors in large commercial, industrial, and residential buildings are usually powered by a central fire alarm system, which is powered by the building power with a battery backup. Domestic smoke detectors range from individual battery-powered units, to several interlinked mains-powered units with battery backup; with these interlinked units, if any unit detects smoke, all trigger even if household power has gone out.

The risk of dying in a home fire is cut in half in homes with working smoke alarms. The US National Fire Protection Association reports 0.53 deaths per 100 fires in homes with working smoke alarms compared to 1.18 deaths in homes without (2009-2013). Some homes don’t have any smoke alarms, some don’t have working batteries; sometimes the alarm fails to detect the fire. [1]

The first automatic electric fire alarm was patented in 1890 by Francis Robbins Upton,[2] an associate of Thomas Edison.[3] George Andrew Darby patented the first European electrical heat detector in 1902 in BirminghamEngland.[4] In the late 1930s Swiss physicist Walter Jaeger tried to invent a sensor for poison gas.[5] He expected that gas entering the sensor would bind to ionized air molecules and thereby alter an electric current in a circuit in the instrument.[5] His device did not meet its purpose: small concentrations of gas had no effect on the sensor’s conductivity.[5] Frustrated, Jaeger lit a cigarette and was soon surprised to notice that a meter on the instrument had registered a drop in current.[6] Smoke particles from his cigarette had apparently done what poison gas could not.[6] Jaeger’s experiment was one of the advances that paved the way for the modern smoke detector.[6] In 1939 Swiss physicist Ernst Meili devised an ionization chamber device capable of detecting combustible gases in mines.[7] He also invented a cold cathode tube that could amplify the small signal generated by the detection mechanism to a strength sufficient to activate an alarm.[7]

Ionization smoke detectors were first sold in the United States in 1951; they were used only in major commercial and industrial facilities in the next several years due to their large size and cost.[7] In 1955 simple home “fire detectors” for homes were developed,[8] detecting high temperatures.[9] The United States Atomic Energy Commission (USAEC) granted the first license to distribute smoke detectors using radioactive material in 1963.[5] The first low-cost smoke detector for domestic use was developed by Duane D. Pearsall in 1965, an individual replaceable battery-powered unit that could be easily installed.[10] The “SmokeGard 700”[11] was a beehive-shaped, strong fire-resistant steel unit.[12] The company began mass-producing these units in 1975.[6] Studies in the 1960s determined that smoke detectors respond to fires much faster than heat detectors

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