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Cable Television HeadendCable television headend is a master facility for receiving television signals for processing and distribution over a cable television system. The headend facility is normally unmanned and surrounded by some type of security fencing and is typically a building or large shed housing electronic equipment used to receive and re-transmit video over the local cable infrastructure. One can also find headends in Power line communication (PLC) substations. Reception The cable TV headend will normally have several large, television receive-only satellite television dishes for reception of cable/satellite TV networks such as ESPN, CNN, or HBO; a dedicated, non-movable dish is required for each satellite that the cable TV utility wishes to receive cable channels off of for distribution over its system. For reception of signals off several adjacent satellites, a larger non-parabolic multi-satellite dish (such as the Torus) that can see up to 3 satellites is often used. Cable TV systems usually also carry local over-the-air television networks for distribution. Since each terrestrial channel represents a defined frequency, a dedicated commercial-grade receiving antenna is needed for each channel that the cable company wishes to receive and distribute. These antennae are often built into a single tower structure called a master antenna television structure. Often, commercial FM pre-amplifiers are used to strengthen weakened terrestrial TV signals as much as possible before distribution. Other sources of programming include those delivered via fiber optics, telephone wires, the Internet, microwave towers and local community access channels that are sent to the cable headend on an outbound frequency over the cable system itself. Signal Processing Once a television signal is received, it must be processed. For satellite TV signals, a dedicated commercial satellite receiver is needed for each channel that is to be distributed by the cable system; these are usually rack-mountable receivers that are designed to take up less space than consumer receivers. Analog terrestrial TV signals do not need a special receiver for reception. Once received, cable television signals are often pre-amplified and then mixed into the cable system's channel numbering scheme using a frequency multiplexer. Once processed, the television signals are sent over the cable system's coaxial cables and continuously re-amplified as needed.
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