User’s Guide 6-4
PID (Program
Identifier)
A code assigned to a unit of data before it leaves the transmitter, based on the program
of which the data is a part, and the type of data, e.g., audio, video, unicast, or multicast.
The term ‘PID’ is also used to refer to the unit of data itself. A typical TV program com-
prises several PIDs.
Polarization Characteristic behavior of the electromagnetic waves. In satellite transmission “linear
polarization” can be horizontal or vertical. Alternatively, there may be “circular polar-
ization” with values of left (also called left hand circular polarization, LHCP) and right
(also called right hand circular polarization, RHCP).
Polarizer Device on the antenna which separates vertically and horizontally polarized waves.
Proxy server (1) On the Internet, a service provider’s computer that acts as an intermediary between
the subscriber’s computer and the data channel to be transmitted. Each data channel has
one or more proxy servers identified by IP address and port.
(2) Software in the subscriber’s computer that communicates with the service provider’s
proxy servers.
QPSK, QAM Modulation schemes for satellite and cable TV, respectively. See Modulation and
Demodulation.
Receiver A machine that tunes and demodulates incoming signal and filters it for desired informa-
tion.
Sampling Conversion of analog signal to numeric data (that can be represented digitally), measur-
ing an electric signal at a predefined pace.
Satellite chart Any free, public source of information about each orbiting satellite—its channels, polar-
ities, symbol rates, and the like.
Satellite database Sky2PC’s database of television and radio programs, as well as antenna settings. This is
the database that is modified when a scan is performed, or when programs are added or
deleted using Program Management. A pre-scanned database ships with Sky2PC in
some cases.
Satellite list The list of satellites available from the satellite database.
Satellite receiver See Receiver.
Switch See LNB Switch.
Symbol Describes radiation that has been modified in phase, amplitude, or other characteristics
in order to represent a signal—especially one consisting of digital information. A Car-
rier Frequency is manipulated into symbols representing information and transmitted.
See also Modulation and Demodulation.
Symbol rate The speed at which the satellite transponder sends symbols, or data, expressed in sym-
bols per second. Different modulation schemes use different symbol rates.
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