Cable television provides a method of delivering television programs to customers by using fiber-optic cables to transmit light pulses or by using coxial cables to send out radio-frequency signals. Cable TV is common in the United States, and customers must subscribe to the cable company to receive service. More than half of the homes in the country have cable television, and most of the viewers are middle-class people living in the suburbs. Rural, inner-city and low-income areas have fewer cable viewers.
Cable broadcasting began in 1924 with radio programming distributed by cable in some cities of Europe. Television broadcasting by cable originated in 1948 when large antennas served entire communities with cables running from the antennas to residents’ homes. Mountainous terrain or distance from transmitters prevented those communities from receiving traditional, over-the-air programming. Because of its origin, many people refer to cable TV as CATV, which stands for Community Antenna Television or Community Access Television.
Receiving cable TV
Local, underground utility lines or aboveground utility poles provide the means for transmitting cable television through distribution lines to each location. Coaxial cable transports the signal to each subscriber through an underground or overhead cable called a service drop. The cable company’s wiring goes to a distribution box located on the exterior of the consumer’s building, and the incoming cable has a small splitter to provide service for different areas of the building. Cable wiring, usually built into the walls, transmits the signal to jacks in various rooms or locations in the building.
Most TV sets in America are cable-ready with television tuners that can receive older, analog cable television service. The cable from a jack in the wall attaches to the connector labeled “Antenna In” on the TV. Most television sets require a digital television adapter that processes digital signals to receive the newer digital cable. The cable company provides the adapter known as a cable converter box, and it connects between the television and the incoming cable. Cable franchise agreements require most companies to provide basic cable including educational channels, community-access channels and local broadcast stations at a low rate.
The cable company has a local distribution facility for each area it serves. A trunkline attached to utility poles originates at the facility, called a headend, and the line distributes to subscribers as many as 500 channels through a coaxial cable. Frequency-division multiplexing is a technique that transmits multiple channels through the cable. The technique translates each television channel to a different frequency at the headend, and there is no interference between separate television signals because each channel has a different frequency on the cable. The television set or a converter box supplied by the company converts the channels back to their original frequencies (basebands) at the subscriber’s location. Earlier analog systems experienced extensive cable theft, so cable companies encrypt the signals of modern digital cable systems. Therefore, subscribers must activate the converter box before it will function. The cable company provides an activation code after the customer signs a contract for the service. Most cable companies provide upstream channels that subscribers can use for sending information to the cable headend to request additional features like cable telephone, cable internet and pay-per-view services. Companies offer different levels of service, from basic to premium, with corresponding monthly fees.
Communication, satellite-dish antennas receive feed signals from television channels at the cable company’s local headend. Cable companies normally include local, community- access channels that focus on local governments, local schools’ educational channels and local broadcast-television stations on their basic cable packages. Programming inserted at the headend may include local businesses’ commercial advertising as well. The individual, nationally distributed channels have nationally oriented commercials.
Modern cable television systems are large, and one network and headend normally serves an entire county or metropolitan area. Most systems carry the signal to local areas from the headend with optical-fiber trunklines. Called hybrid-fiber coaxial distribution, the trunklines allow for future expansion and greater bandwidth as well. The company uses a light beam at the headend to modulate the radio-frequency, electrical signal transmitting the channels and sends it through the fiber. The fiber trunkline runs to distribution hubs where numerous fibers spread out and take the signal to optical nodes located in local communities. The fiber’s light beam translates back into an electrical signal at the optical node, and coaxial cable-distribution lines attached to utility poles carry the signal to subscribers.
Live television programming on cable
Cable-originated, live television programming began with regulations mandated in the 1980s, similar to those for government-access, public and educational channels. The programming developed into today’s broadcasts of cable-only, produced miniseries and television movies along with a large variety of cable-only, live broadcasts offered by many cable networks. Most of the United States major television markets began producing live, local-interest programs early in the 1980s. Replacement of most regulations began near the end of the last century with the Internet’s advancement and development of new technologies in the industry. Consumers now have various options for viewing local programming, including bundled digital-cable, Internet and phone service.