In telecommunications, a logical channel number (LCN), also known as virtual channel as used in ATSC SI data, is a channel designation which differs from that of the actual radio channel (or range of frequencies) on which the signal travels.
The term is most often applied to television, where digital television (DTV) channels may operate on different physical channels from the displayed channels. A station branded as Channel 8, for example, might actually use channel 32 for its ATSC, DVB or ISDB transmission, but a virtual channel map or virtual channel table (VCT) allows viewers to tune in the station on channel 8, displayed as 8.1 on a digital set. DTV tuners have a menu item that scans all channels for this information and stores it in memory for instant access later on.
The most common reason for a television station using a virtual channel is to minimize viewer confusion when a digital transmission is airing on a different channel from the one the station used in analog mode. The virtual channel thus enables viewers to tune in the station by choosing the same channel number as they would have previously. In the case of pay TV and joint broadcaster services such as Freeview the channel number is also a way of locking in the ordering of channels to an order that suits the provider rather than to what the viewer may prefer.
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