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Glossary
P
R
P
B
Analogue Color difference signals. Refer to C
R
C
B
for an explanation.
PROM Programmable Read-Only Memory: A device, which may be written
once with data for permanent storage, and then read whenever
required. Special types of PROM permit the erasure of all data by
Ultraviolet light (EPROM) or by application of an electronic signal
(EEPROM).
PS Program Stream: A combination of one or more PESs with a
common timebase.
PSI Program Specific Information: Consists of normative data, which is
necessary for the de-multiplexing of transport streams and the
successful regeneration of programs (see also: SI).
PSIP Program System Information Protocol: The ATSC equivalent of SI
for DVB.
PSK Phase Shift Keying: A method of modulating digital signals
particularly suited to satellite transmission.
PSR
Professional Satellite Receiver: See also: IRD.
PSU
Power Supply Unit.
QAM Quadrature Amplitude Modulation: A method of modulating digital
signals, which uses combined techniques of phase modulation and
amplitude modulation. It is particularly suited to cable networks.
QoS Quality of Service. A common term for a set of parameters
describing the quality you get from an IP network: Throughput,
availability, delay, jitter and packet loss.
QPSK Quadrature Phase Shift Keying: A form of phase shift keying
modulation using four states.
QSIF
Quarter Screen Image Format.
Quantise A process of converting analogue waveforms to digital information.
8-bit quantization as set out in ITU-R Rec. 601. Uses 256 levels in
the range 0 – 255 to determine the analogue waveform value at any
given point. The value is then converted to a digital number for
processing in the digital domain.
RAM Random Access Memory: A volatile storage device for digital data.
Data may be written to, or read from, the device as often as
required. When power is removed, the data it contains is lost.
RAS Remote Authorization System: A Ericsson AB proprietary public-key
encryption system used to prevent unauthorized viewing of a TV
programme or programmes.
RF
Radio Frequency.
RGB
Red, Green, Blue: The Chroma information in a video signal.
RIP2 Routing Information Protocol v2. A protocol used between network
routers to exchange routing tables and information.
EN/LZT 790 0003/2 R1A
A-15