Cable
television is a way of letting people watch television without having to get
signals from an antenna. The television signals are brought to the television
through a coaxial cable. People usually have to pay to subscribe to cable
television. With cable television, people can watch hundreds of television
channels carrying many television shows. Usually some of these are television
stations and others are made for the cable companies.
Cable
TV is provided by many carriers in across with world. Some of those carriers in
the United States are: AT&T U-Verse, CableVision, Comcast, Cox
Communications, SuddenLink, Time Warner Cable and Verizon
Another
method of subscription television is by Satellite television, especially in
places where cable TV is not available.
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Cable
television is a system of delivering television programming to consumers via
radio frequency (RF) signals transmitted through coaxial cables, or in more
recent systems, light pulses through fiber-optic cables. This contrasts with
broadcast television (also known as terrestrial television), in which the
television signal is transmitted over the air by radio wavesand received by a
television antenna attached to the television; or satellite television, in
which the television signal is transmitted by a communications satellite
orbiting the Earth and received by a satellite dish on the roof. FM radio
programming, high-speed Internet, telephone services, and similar
non-television services may also be provided through these cables. Analog
television was standard in the 20th century, but since the 2000s, cable systems
have been upgraded to digital cable operation.
A
"cable channel" (sometimes known as a "cable network") is a
television network available via cable television. When available through
satellite television, including direct broadcast satellite providers such as
DirecTV, Dish Network and Sky, as well as via IPTV providers such as Verizon
FIOS and AT&T U-verse is referred to as a "satellite channel".
Alternative terms include "non-broadcast channel" or
"programming service", the latter being mainly used in legal contexts.
Examples of cable/satellite channels/cable networks available in many countries
are HBO, Cinemax, MTV, Cartoon Network, AXN, E!, Fox Life, Discovery Channel,
Canal+, Eurosport, Fox Sports, Disney Channel, Nickelodeon, CNN International,
ESPN, GMA Pinoy TV and The Filipino Channel.
The
abbreviation CATV is often used for cable television. It originally stood for
Community Access Television or Community Antenna Television, from cable
television's origins in 1948. In areas where over-the-air TV reception was
limited by distance from transmitters or mountainous terrain, large
"community antennas" were constructed, and cable was run from them to
individual homes. The origins of cable broadcasting for radio are even older as
radio programming was distributed by cable in some European cities as far back
as 1924.
History in North
America
Cable
television began in the United States as a commercial business in 1950,
although there were small-scale systems by hobbyists in the 1940s.
The
early systems simply received weak (broadcast) channels, amplified them, and
sent them over unshielded wires to the subscribers, limited to a community or
to adjacent communities. The receiving antenna would be higher than any
individual subscriber could afford, thus bringing in stronger signals; in hilly
or mountainous terrain it would be placed at a high elevation.
At
the outset, cable systems only served smaller communities without television
stations of their own, and which could not easily receive signals from stations
in cities because of distance or hilly terrain. In Canada, however, communities
with their own signals were fertile cable markets, as viewers wanted to receive
American signals. Rarely, as in the college town of Alfred, New York, U.S.
cable systems retransmitted Canadian channels.
Although
early (VHF) television receivers could receive 12 channels (2-13), the maximum
number of channels that could be broadcast in one city was 7: channels 2, 4,
either 5 or 6, 7, 9, 11 and 13, as receivers at the time were unable to receive
strong (local) signals on adjacent channels without distortion. (There were
frequency gaps between 4 and 5, and between 6 and 7, which allowed both to be
used in the same city).
As
equipment improved, all twelve channels could be utilized, except where a local
VHF television station broadcast. Local broadcast channels were not usable for
signals deemed to be priority, but technology allowed low-priority signals to
be placed on such channels by synchronizing their blanking intervals.
Similarly, a local VHF station could not be carried on its broadcast channel as
the signals would arrive at the TV set slightly separated in time, causing
"ghosting".
The
bandwidth of the amplifiers also was limited, meaning frequencies over 250 MHz
were difficult to transmit to distant portions of the coaxial network, and UHF
channels could not be used at all. To expand beyond 12 channels, non-standard
"midband" channels had to be used, located between the FM band and
Channel 7, or "superband" beyond Channel 13 up to about 300 MHz;
these channels initially were only accessible using separate tuner boxes that
sent the chosen channel into the TV set on Channel 2, 3 or 4.
Before
being added to the cable box itself, these midband channels were used for early
incarnations of pay TV, e.g. The Z Channel(Los Angeles) and HBO but transmitted
in the clear i.e. not scrambled as standard TV sets of the period could not
pick up the signal nor could the average consumer `de-tune' the normal stations
to be able to receive it.
Once
tuners that could receive select mid-band and super-band channels began to be
incorporated into standard television sets, broadcasters were forced to either
install scrambling circuitry or move these signals further out of the range of
reception for early cable-ready TVs and VCRs. However, once all 181 allocated
cable channels had been incorporated, premium broadcasters were left with no
choice but to scramble.
Unfortunately
for pay-TV operators, the descrambling circuitry was often published in
electronics hobby magazines such as Popular Science and Popular Electronics
allowing anybody with anything more than a rudimentary knowledge of broadcast
electronics to be able to build their own and receive the programming without
cost.
Later,
the cable operators began to carry FM radio stations, and encouraged
subscribers to connect their FM stereo sets to cable. Before stereo and
bilingual TV sound became common, Pay-TV channel sound was added to the FM
stereo cable line-ups. About this time, operators expanded beyond the
12-channel dial to use the "midband" and "superband" VHF
channels adjacent to the "high band" 7-13 of North American
television frequencies. Some operators as in Cornwall, Ontario, used a dual
distribution network with Channels 2-13 on each of the two cables.
During
the 1980s, United States regulations not unlike public, educational, and
government access (PEG) created the beginning of cable-originated live
television programming. As cable penetration increased, numerous cable-only TV
stations were launched, many with their own news bureaus that could provide
more immediate and more localized content than that provided by the nearest
network newscast.
Such
stations may use similar on-air branding as that used by the nearby broadcast
network affiliate, but the fact that these stations do not broadcast over the
air and are not regulated by the FCC, their call signs are meaningless. These
stations evolved partially into today's over-the-air digital subchannels, where
a main broadcast TV station e.g. NBS 37* would – in the case of no local CNB or
ABS station being available – rebroadcast the programming from a nearby
affiliate but fill in with its own news and other community programming to suit
its own locale. Many live local programs with local interests were subsequently
created all over the United States in most major television markets in the
early 1980s.
This
evolved into today's many cable-only broadcasts of diverse programming,
including cable-only produced television moviesand miniseries. Cable specialty
channels, starting with channels oriented to show movies and large sporting or
performance events, diversified further, and "narrowcasting" became
common. By the late 1980s, cable-only signals outnumbered broadcast signals on
cable systems, some of which by this time had expanded beyond 35 channels. By
the mid-1980s in Canada, cable operators were allowed by the regulators to
enter into distribution contracts with cable networks on their own.
By
the 1990s, tiers became common, with customers able to subscribe to different
tiers to obtain different selections of additional channels above the basic
selection. By subscribing to additional tiers, customers could get specialty
channels, movie channels, and foreign channels. Large cable companies used
addressable descramblers to limit access to premium channels for customers not
subscribing to higher tiers, however the above magazines often published
workarounds for that technology as well.
During
the 1990s, the pressure to accommodate the growing array of offerings resulted
in digital transmission that made more efficient use of the VHF signal
capacity; fibre optics was common to carry signals into areas near the home,
where coax could carry higher frequencies over the short remaining distance.
Although for a time in the 1980s and 1990s, television receivers and VCRs were
equipped to receive the mid-band and super-band channels. Due to the fact that
the descrambling circuitry was for a time present in these tuners, depriving
the cable operator of much of their revenue, such cable-ready tuners are rarely
used now - requiring a return to the set-top boxes used from the 1970s onward.
The
conversion to digital broadcasting has put all signals - broadcast and cable -
into digital form, rendering analog cable television service mostly obsolete,
functional in an ever-dwindling supply of select markets. Analog television
sets are still[when?]accommodated, but their tuners are mostly obsolete,
oftentimes dependent entirely on the set-top box.
Deployments by continent
Cable
television is mostly available in North America, Europe, Australia, South Asia
and East Asia, and less so in South America and the Middle East. Cable
television has had little success in Africa, as it is not cost-effective to lay
cables in sparsely populated areas. So-called "wireless cable" or
microwave-based systems are used instead.
Cable
television, generally, any system that distributes television signals by means
of coaxial or fibre-optic cables. The term also includes systems that distribute
signals solely via satellite. Cable-television systems originated in the United
States in the late 1940s and were designed to improve reception of commercial
network broadcasts in remote and hilly areas. During the 1960s they were
introduced in many large metropolitan areas where local television reception is
degraded by the reflection of signals from tall buildings. Commonly known as
community antenna television (CATV), these cable systems use a “community
antenna” to receive broadcast signals (often from communications satellites),
which they then retransmit via cables to homes and establishments in the local
area subscribing to the service. Subscribers pay a specified monthly service
charge in addition to an initial installation fee.
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Source:
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