A collection of contiguous bits of data.
A sequential flow of data packets.
Data transmission method that divides messages into standard-sized packets for greater efficiency of routing and transport through a network.PAL - Phase Alternation System
The German developed TV standard based upon 50 cycles per second and 625 lines.
The most frequently found satellite TV antenna, it takes its name from the shape of the dish described mathematically as a parabola. The function of the parabolic shape is to focus the weak microwave signal hitting the surface of the dish into a single focal point in front of the dish. It is at this point that the feedhorn is usually located.Phase-Locked Loop (PLL)
A type of electronic circuit used to demodulate satellite signals.PID - Packet identifier.
PIDAC - Packet Initiated Data Access Control.
This is the DigiCipher I upgrade module.Polarization
A technique used by the satellite designers to increase the capacity of the satellite transmission channels by reusing the satellite transponder frequencies. In linear cross polarization schemes, half of the transponders beam their signals to earth in a vertically polarized mode; the other half horizontally polarize their down links. Although the two sets of frequencies overlap, they are 90 degree out of phase, and will not interfere with each other. To successfully receive and decode these signals on earth, the earth station must be outfitted with a properly polarized feedhorn to select the vertically or horizontally polarized signals as desired.
In some installations, the feedhorn has the capability of receiving the vertical and horizontal transponder signals simultaneously, and routing them into separate LNAs for delivery to two or more satellite television receivers. Unlike most domestic satellites, the Intelsat series of satellites use a technique known as left-hand and right-hand circular polarization.Polarization Rotator
A device that can be manually or automatically adjusted to select one of two orthogonal polarizations.
Antenna mechanism permitting steering in both elevation and azimuth through rotation about a single axis. While an astronomer's polar mount has its axis parallel to that of the earth, satellite earth stations utilize a modified polar mount geometry that incorporates a declination offset.
An orbit with its plane aligned in parallel with the polar axis of the earth.PTT - Post Telephone and Telegraph Administration
Refers to operating agencies directly or indirectly controlled by governments in charge of telecommunications services in most countries of the world.
Pulse Code Modulation
A time division modulation technique in which analog signals are sampled and quantized at periodic intervals into digital signals. The values observed are typically represented by a coded arrangement of 8 bits of which one may be for parity.
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