Specifications

Glossary
Term Description
OQPSK Offset Quadrature Phase Shift Keying: A variant of phase-shift keying
modulation using 4 different values of the phase to transmit. It is
sometimes called Staggered quadrature phase-shift keying (SQPSK).
OSD On-screen display: Messages and graphics, typically originating from the
SMS, and displayed on the subscriber’s TV screen by the IRD, to inform
the subscriber of problems or instruct the subscriber to contact the SMS.
PCM Pulse Code Modulation: A process in which a signal is sampled, each
sample is quantised independently of other samples, and the resulting
succession of quantised values is encoded into a digital signal.
PCR Program Clock Reference: A time-stamp in the transport stream from
which the Decoder timing is derived.
PES Packetised Elementary Stream: A sequential stream of data bytes that
has been converted from original elementary streams of audio and
video access units and transported as packets. Each PES packet consists
of a header and a payload of variable length and subject to a
maximum of 64 kbytes. A time-stamp is provided by the MPEG-2 systems
layer to ensure correct synchronisation between related elementary
streams at the Decoder.
PID Packet Identifier: The header on a packet in an elementary data stream,
which identifies that data stream. An MPEG-2 / DVB standard.
PLL Phase-Locked Loop. A phase-locked loop is a control system which
controls the rotation of an object by comparing its rotational position
(phase) with another rotating object as in the case of a sine wave or
other repeating signal. This type of control system can synchronise not
only the speed, but also the angular position of two waveforms that are
not derived from the same source.
Program PC - A sequence of instructions for a computer.
TV - A concept having a precise definition within ISO 13818-1 (MPEG-2).
For a transport stream, the timebase is defined by the PCR. The use of the
PCR for timing information creates a virtual channel within the stream.
Programme A linking of one or more events under the control of a broadcaster. For
example, football match, news, film show. In the MPEG-2 concept, the
collection of elementary streams comprising the programme, have a
common start and end time. A series of programmes are referred to as
events.
PS Program Stream: A combination of one or more PESs with a common
timebase.
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.
SBM75e Series Modulator Installation and Operation Manual
B-9