Cable TV

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Cable television is a system of providing television, FM radio programming and other services to consumers via radio frequency signals transmitted directly to people’s televisions through fixed optical fibers or coaxial cables as opposed to the over-the-air method used in traditional television broadcasting (via radio waves) in which a television antenna is required.

It should be noted that while the acronym CATV is often used to mean "Cable TV" or "Community Access Television," it originally stood for Community Antenna Television. This comes from cable television's origins in 1938, when the first cable systems were started. Television signals could only be received by homes that were in the "line-of-sight" of the originating broadcast antenna, and people in mountainous areas could not receive the signal. Large antennas were constructed in these areas, and cable was run from the antenna to homes so they could receive programming, making these large antennas "community antennas."

It is most commonplace in North America, Europe, Australia and East Asia, though it is present in many other countries, mainly in South America and the Middle East. Cable TV has had little success in Africa, as it is not cost-effective to lay cables in sparsely populated areas, and although so-called "wireless cable" or microwave-based systems are used, "direct-to-home" satellite television is far more popular, especially in South Africa.

Technology

Technically, CATV involves distributing a number of television channels collected at a central location (called a headend) to subscribers within a community by means of a branched network of optical fibers and/or coaxial cables and broadband amplifiers. Since the early 1990s, the most common architecture is the Hybrid fiber coaxial network.

As in the case of radio broadcasting, the use of different frequencies allows many channels to be distributed through the same cable, without separate wires for each. A Set-top box or the tuner of the TV, VCR or radio selects one channel from this mixed signal.

The same program is often simultaneously broadcast by radio and distributed by cable, usually at different frequencies. Other programs may be distributed by cable only; rules restricting content (e.g. regarding nudity and pornography) are often more relaxed for cable than for over-the-air TV.

Traditional cable TV systems worked strictly by way of analog signals (i.e. using standard radio waves) but many modern cable TV systems also employ the use of digital cable technology, which uses compressed digital signals, allowing them to provide many more channels than they could with analog alone. Modern cable TV systems also offer other services such as Video on demand, telephony, and high-speed data.

Read more at Wikipedia.org