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A television channel is a physical or virtual channel over which a television station or television network is distributed. For example, in North America, "channel 2" refers to the broadcast or cable band of 54 to 60 MHz, with carrier frequencies of 55.25 MHz for NTSC analog video (VSB) and 59.75 MHz for analog audio (FM), or 55.31 MHz for digital ATSC (8VSB). Channels may be shared by many different television stations or cable-distributed channels depending on the location and service provider. Depending on the multinational bandplan for a given region, analog television channels are typically 6, 7, or 8 MHz in bandwidth, and therefore television channel frequencies vary as well. Channel numbering is also different. Digital television channels are the same for legacy reasons, however through multiplexing, each physical radio frequency (RF) channel can carry several digital subchannels. On satellites, each transponder normally carries one channel, however small, independent channels can be used on each transponder, with some loss of bandwidth due to the need for guard bands between unrelated transmissions. ISDB, used in Japan and Brazil, has a similar segmented mode. Channel separation on over-the-air channels is accomplished by skipping at least one channel between two analog stations' frequency allocations. (There can be gaps between channels, where numbers are sequential, but frequencies are not contiguous, such as the skip from VHF low to high, and the jump to UHF.) On cable TV, it is possible to use adjacent channels only because they are all at the same power, something which could only be done over the air if the two stations were transmitted at the same power and height from the same location. For digital TV, selectivity is inherently better, therefore channels adjacent (either to analog or digital stations) can be used even in the same area. ==Other meanings== Commonly, the term "television channel" is used to refer to either a terrestrial television station or its cable/satellite counterpart (both outlined below). Sometimes, especially outside the U.S. and in the context of cable/satellite television, it is used instead of the term television network, which otherwise (in its technical use above) describes a group of geographically-distributed television stations that share affiliation/ownership and some or all of their programming with one another. This terminology may be muddled somewhat in other jurisdictions, for instance Europe, where terrestrial channels are commonly mapped from physical channels to common numerical positions (i.e. BBC One does not broadcast on any particular "channel 1" but is nonetheless mapped to the "1" input on most British television sets). On digital platforms, such (location) channels are usually arbitrary and changeable, due to virtual channels. 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「Television channel」の詳細全文を読む スポンサード リンク
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