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Avalanche transceivers or avalanche beacon are a class of active radio beacon transceivers operating at 457 kHz and specialized for the purpose of finding people or equipment buried under snow. When the owner sets out on a skiing descent, the transceiver is activated, causing the device to emit a low-power pulsed beacon signal during the trip.〔 Following an avalanche, and if the holder of the transceiver is safe and has not themselves been caught by the avalanche, they may switch the transceiver from transmit into receive mode, allowing use as a radio direction finding device to search for signals coming from other skiers' transmitter beacons who may be trapped. A 457 kHz beacon is an active device that requires batteries. A ski suit may also contain a passive RECCO transponder sewn into the clothing. Early avalanche beacons transmitted at 2.275 kHz (2275 Hz).〔 In 1986, the international frequency standard of 457 kHz was adopted, and this remains the standard today.〔 Many companies manufacture beacons that comply with this standard. An avalanche beacon is not considered a preventive measure against possible avalanche burial, but rather it is a way to reduce the amount of time buried.〔 ==History== In 1968, Dr. John Lawton invented the first effective avalanche transceiver〔 at Cornell Aeronautical Laboratory in Buffalo, New York, with the first units being sold in 1971 under the “Skadi” brand name.〔 This unit, functioning at 2.275 kHz, converted the radio frequency to a simple tone audible to the human ear. By following the tone to where it was loudest, the beacon operator could use it to locate the buried beacon by using a grid searching technique.〔 In 1986, IKAR adopted the frequency of 457 kHz. In 1996 ASTM adopted the 457 kHz standard.〔 The following are the currently accepted international standards for Avalanche Transceivers operating on the 457 kHz frequency.〔〔〔〔 * 457 kHz, frequency tolerance ±80 Hz * 200 hours transmitting at +10C (assumed inside protective clothing) * 1 hours receiving at −10C (assumed handheld) * operation from −20C to +45C * carrier keying (pulse period) 1000±300 ms Now that the frequency 457 kHz had become an international standard, and the problems of range had been discussed and analyzed, everyone was most interested in ease of use. With a new generation of entirely automatic apparatuses existing on the market containing a microprocessor that analyzed the beacon's signals or pulses to determine both the direction and distance of the victim, a new digital age was born. In 1997, the first digital beacon was introduced at the Winter Outdoor Retailer show by Backcountry Access under the brand name "Tracker".〔 The Tracker DTS soon became the most widely used beacon in North America, and is still sold and used by many backcountry enthusiasts. Today, consumers have a wide range of choices for digital beacons from companies like Ortovox, Arva, Pieps, Mammut, and Backcountry Access. Although beacon technology is constantly evolving and improving, practicing and being familiar with your beacon remains the most important aspect for performing timely rescues and preventing avalanche fatalities. 抄文引用元・出典: フリー百科事典『 ウィキペディア（Wikipedia）』 ■ウィキペディアで「Avalanche transceiver」の詳細全文を読む スポンサード リンク
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