Cable television
Alternative terms include non-broadcast channel or programming service, the latter being mainly used in legal contexts.
[4] 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.
Subscribers can choose from several levels of service, with premium packages including more channels but costing a higher rate.
At the local headend, the feed signals from the individual television channels are received by dish antennas from communication satellites.
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 trunklines that carry the signal from the headend to local neighborhoods are optical fiber to provide greater bandwidth and also extra capacity for future expansion.
The receiving antenna would be taller than any individual subscriber could afford, thus bringing in stronger signals; in hilly or mountainous terrain it would be placed at a high elevation.
Rarely, as in the college town of Alfred, New York, U.S. cable systems retransmitted Canadian channels.
TVs were unable to reconcile these blanking intervals and the slight changes due to travel through a medium, 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.
[citation needed] Initially, UHF broadcast stations were at a disadvantage because the standard TV sets in use at the time were unable to receive their channels.
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 consumer sets had the ability to receive all 181 FCC allocated channels, premium broadcasters were left with no choice but to scramble.
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.
During the 1980s, United States regulations not unlike public, educational, and government access (PEG) created the beginning of cable-originated live television programming.
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.
Analog television sets are accommodated, their tuners mostly obsolete and dependent entirely on the set-top box.
Coaxial cables are capable of bi-directional carriage of signals as well as the transmission of large amounts of data.
This limited the upstream speed to 31.2 Kbp/s and prevented the always-on convenience broadband internet typically provides.
The combination of television, telephone and Internet access is commonly called triple play, regardless of whether CATV or telcos offer it.
