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Leaky feeder
A leaky feeder is a communications system used in underground mining and other tunnel environments. The layman's term "leaky feeder" implies that the cable is in some way deficient. Manufacturers and cabling professionals use the term "radiating cable"〔(【引用サイトリンク】Times Microwave Radiating Cable Catalogue )">website=Times Microwave )〕 〔(【引用サイトリンク】website=Commscope )〕 〔(【引用サイトリンク】url=http://www.rfsworld.com/stayconnected/index.php?p=657&l=1&listName=stayconnected_en_articles&indexVal=744 )〕 as this implies that the cable is designed to radiate: something that coaxial cable is not generally supposed to do.
== Principle of operation ==
A ''leaky feeder'' communication system consists of a coaxial cable run along tunnels which emits and receives radio waves, functioning as an extended antenna. The cable is "leaky" in that it has gaps or slots in its outer conductor to allow the radio signal to leak into or out of the cable along its entire length. Because of this leakage of signal, line amplifiers are required to be inserted at regular intervals, typically every 350 to 500 metres, to boost the signal back up to acceptable levels. The signal is usually picked up by portable transceivers carried by personnel. Transmissions from the transceivers are picked up by the feeder and carried to other parts of the tunnel, allowing two-way radio communication throughout the tunnel system.
The system has a limited range and because of the frequency it uses (typically VHF or UHF), transmissions cannot pass through solid rock, which limits the system to a line-of-sight application. It does, however, allow two-way mobile communication.
抄文引用元・出典: フリー百科事典『 ウィキペディア（Wikipedia）』
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