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| Home ยป Custom Services » CablePak » How Cable Works |
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How cable Works |
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The Headend
The control center of a cable television system, the headend receives
incoming signals from satellites, television antennas and locally
produced programs and amplifies, converts, processes, combines and
transmits the signals through a cable network to subscribers. The
headend includes antennas, preamplifiers, frequency converters,
demodulators, modulators, processors, scrambling and descrambling
equipment. |
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The uplink sends programming
signals to satellites to be relayed back to earth. Cable programmers
have large uplinks, which are more powerful than, but similar to
earth stations.
Relays signals sent from transmitting antennas (uplinks) back down to the Earth's surface. Communication satellites are in
a geostationary orbit 22,300 miles above the Earth, revolving in
synchronization with the Earth's rotation. The parts of the satellite
used for receiving and transmitting signals are called transponders,
an acronym for transmitter and responder. |
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Earth Stations receive satellite signals. This parabolic antenna is also
known as a TVRO (Television Receive Only) antenna. A number of earth
stations are located at the cable system to receive programming
from dozens of services like MTV, ESPN and HBO. Also called "dishes"
because of its shape, earth stations can be 15 meters or more in
diameter, or as small as 18 inches. Millions of individuals and
businesses also own dishes to receive programming directly from
satellites. |
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A network of coaxial cable and fiber optic cable used by cable providers to deliver programming
to customers. A broadband cable system is capable of delivering
analog and digital communication signals. The first segment, the
trunk line system, connects the headend to the first bridging amplifiers
or fiber optic nodes. Trunk lines can also include power supplies
and other electronic components. The next segment, the feeder system,
carries signals to individual neighborhoods. The last segment, the
drop line part of the network, is coaxial cable which connects individual
subscriber locations to the feeder trunk. |
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| Reprinted with permission from the Cable Center. |
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