Cable tv network

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 fibre-optic cables. This contrasts with broadcast television (also known as terrestrial television), in which the television signal is transmitted over the air by radio waves and received by a television antenna attached to the television;

1. Cable TV Network 
 
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 
fibre-optic cables. This contrasts with broadcast television (also 
known as terrestrial television), in which the television signal is 
transmitted ​over the air by radio waves and 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 

2. since the 2000s, cable systems have been upgraded to digital cable 
operation. 
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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, this 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!, FX, Discovery Channel, 
Canal+, Eurosport, Fox Sports, Disney Channel, Nickelodeon, CNN 
International, and ESPN. 
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 

3. homes. In 1968 6.4 % of Americans had cable television. The 
number increased to 7.5% in 1978. By 1988 52.8 % of all households 
were using cable. The number further increased to 62.4 % in 1994. 
 
Distribution  
 
To receive cable television at a given location, cable distribution 
lines must be available on the local utility poles or underground 
utility lines. Coaxial cable brings the signal to the customer's 
building through a service drop, an overhead or underground cable. 
If the subscriber's building does not have a cable service drop, the 

4. cable company will install one. The standard cable used in the U.S. 
is RG-6, which has a 75 ohm impedance, and connects with a type F 
connector. The cable company's portion of the wiring usually ends 
at a distribution box on the building exterior, and built-in cable 
wiring in the walls usually distributes the signal to jacks in different 
rooms to which televisions are connected. Multiple cables to 
different rooms are split off the incoming cable with a small device 
called a splitter. There are two standards for cable television; older 
analog cable, and newer digital cable which can carry data signals 
used by digital television receivers such as HDTV equipment. All 
cable companies in the United States have switched to or are in the 
course of switching to digital cable television since it was first 
introduced in the late 1990s. 
 

5. Most cable companies require a set-top box or a slot on one's TV set 
for conditional access module cards to view their cable channels, 
even on newer televisions with digital cable QAM tuners, because 
most digital cable channels are now encrypted, or "scrambled", to 
reduce cable service theft. A cable from the jack in the wall is 
attached to the input of the box, and an output cable from the box is 
attached to the television, usually the RF-IN or composite input on 
older TVs. Since the set-top box only decodes the single channel 
that is being watched, each television in the house requires a 
separate box. Some unencrypted channels, usually traditional 
over-the-air broadcast networks, can be displayed without a 
receiver box. The cable company will provide set top boxes based on 
the level of service a customer purchases, from basic set top boxes 
with a standard definition picture connected through the standard 
coaxial connection on the TV, to high-definition wireless DVR 
receivers connected via HDMI or component. Older analog 
television sets are "cable ready" and can receive the old analog 
cable without a set-top box. To receive digital cable channels on an 
analog television set, even unencrypted ones, requires a different 
type of box, a digital television adapter supplied by the cable 
company or purchased by the subscriber. Another new distribution 
method that takes advantage of the low cost high quality DVB 
distribution to residential areas, uses TV gateways to convert the 

6. DVB-C, DVB-C2 stream to IP for distribution of TV over IP network 
in the home. 
Principle of operation  
 
In the most common system, multiple television channels (as many 
as 500, although this varies depending on the provider's available 
channel capacity) are distributed to subscriber residences through a 
coaxial cable, which comes from a trunkline supported on utility 
poles originating at the cable company's local distribution facility, 
called the "headend". Many channels can be transmitted through 
one coaxial cable by a technique called frequency division 
multiplexing. At the end, each television channel is translated to a 
different frequency. By giving each channel a different frequency 

7. "slot" on the ​cable​, the separate ​television ​signals do not interfere 
with each other. At an outdoor cable box on the subscriber's 
residence the company's service drop cable is connected to cables 
distributing the signal to different rooms in the building. At each 
television, the subscriber's television or a set-top box provided by 
the cable company translates the desired channel back to its 
original frequency (baseband), and it is displayed on screen. Due to 
widespread cable theft in earlier analog systems, the signals are 
typically ​encrypted ​on modern digital cable systems, and the 
set-top box must be activated by an activation code sent by the 
cable company before it will function, which is only sent after the 
subscriber signs up. If the subscriber fails to pay their bill, the cable 
company can send a signal to deactivate the subscriber's box, 
preventing reception. 
There are also usually "​upstream​" channels on the cable to send 
data from the customer box to the cable headend, for advanced 
features such as requesting pay-per-view shows or movies, cable 
internet access, and cable telephone service. The "downstream" 
channels occupy a band of frequencies from approximately 50 MHz 
to 1 GHz, while the "upstream" channels occupy frequencies of 5 to 
42 MHz. Subscribers pay with a monthly fee. Subscribers can 
choose from several levels of service, with "premium" packages 
including more channels but costing a higher rate. At the local 

8. headend, the feed signals from the individual television channels 
are received by dish antennas from communication satellites. 
Additional local channels, such as local broadcast television 
stations, educational channels from local colleges, and community 
access channels devoted to local governments (PEG channels) are 
usually included on the cable service. Commercial advertisements 
for local business are also inserted in the programming at the 
headend (the individual channels, which are distributed nationally, 
also have their own nationally oriented commercials). 
Hybrid fiber-coaxial 
 
Main article: Hybrid fibre-coaxial 
Modern cable systems are large, with a single network and headend 
often serving an entire metropolitan area. Most systems use hybrid 
fiber-coaxial (HFC) ​distribution​; this means the trunk lines that 

9. carry the signal from the ​headend ​to local neighborhoods are 
optical fiber to provide greater bandwidth and also extra capacity 
for future expansion. At the headend, the electrical signal is 
translated into an optical signal and sent through the fiber. The 
fiber trunkline goes to several distribution hubs, from which 
multiple fibers fan out to carry the signal to boxes called optical 
nodes in local communities. At the optical node, the optical signal is 
translated back into an electrical signal and carried by coaxial cable 
distribution lines on utility poles, from which cables branch out to a 
series of signal amplifiers and line extenders. These devices carry 
the signal to customers via passive RF devices called taps.