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Glossary, abbreviations
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Glossary, abbreviations
DiSEqC
DiSEqC (Digital Satellite Equipment Control) is a
EUTELSAT-specified communications system
between sat. receiver (master) and the peripheral
sat. components (slaves) such as, for example,
LNBs, multiswitches, rotatable antenna systems.
DiSEqC is a single master / multi slave system, i.e.
there is always only one master in the sat. system.
All activities are always initiated by the master.
DiSEqC components
If DiSEqC switching matrices are connected in
cascade, the master receiver must send out the
DiSEqC signal repeatedly, in order that all DiSEqC
multiswitches in the cascade receive their
commands.
DiSEqC components (slaves) need to be
downward compatible nowadays, i.e. they must
also respond to the analogue switching criteria of
receivers that are only equipped with H/V and 22
kHz control signals.
A DiSEqC switching matrix keeps working with
analogue switching criteria until the DiSEqC
command arrives from the master. After this all
analogue switching criteria are ignored.
DVB MPEG-2
DVB is the abbreviation for Digital Video
Broadcasting. DVB-S indicates the type of
transmission. (S=Satellite). MPEG is an
abbreviation for Moving Picture Experts Group, a
working group that sets out internationally
applicable standards for digital compression of
video, along with audio. MPEG-2 has been
elevated to the standard for compression of digital
TV signals. MPEG-2 works up to a data rate of 100
Mbit/s.
Eb/No ratio
The Eb/No ratio is a measure for the signal-to-
noise ratio of digital signals. This value is not
identical to the S/N value known from analogue
receiving technology. With Eb/No values below
5dB reception is generally no longer possible.
FEC
FEC is an abbreviation for Forward Error
Correction. The FEC error rate corresponds to the
Viterbi rate.
PID
The PID number (Packed IDentification) is an
identification number for video signals and audio
signals in the digital data stream of DVB MPEG-2-
signals. With the PID number, the receiver
establishes a unique assignment of the video- and
audio data transmission. The PID-PCR is the
identification number for the synchronisation
signal. The PID-PCR is generally identical to the
PID video. With programmes broadcast in several
languages, the audio PID of another language of
the TV broadcast can be assigned through manual
entry. After entry of the PID, the digital receiver
automatically fetches from the data stream the
audio data identified through the PID number and
assigns this to the video signal.
Programme package
A digital transponder‘s programme package mostly
contains several TV and radio programmes. Every
programme package has a fixed relationship to the
transponder transmission frequency, polarisation
(horizontal or vertical), to the symbol rate and to
the Viterbi rate or error rate.
Symbol rate
The symbol rate describes the amount of data that
is transmitted per second. It is measured in
Msymbols/s and is equal to the number of symbols
that arrive per second.
Transponder
A transponder is a transmitter in the satellite that
transmits TV and radio signals on a high
transmission frequency to the sat. receiving
antennas. A satellite has a number of
transponders.
Transponder, analogue
An analogue broadcasting transponder always
transmits only one TV programme and possibly a
number of radio programs on its transmission
frequency..
Transponder, digital
A digital broadcasting transponder is able to
transmit several TV and several radio programs
simultaneously on its transmission frequency.
When a program provider beams down several TV
programs via a digital transponder, one then also
talks of the program provider’s “program package”
The terms “Digital transponder” and “Program
package” have the same meaning.
Video bit rate
The video bit rate describes the amount of
digitalized video signal data that is transmitted per
second.
Viterbi rate
The Viterbi rate (code rate, error rate)
characterises the error protection used by the
program provider. The DVB standard has
earmarked the following values: 1/2 - 2/3 – 3/4 -
4/5 – 5/6 – 6/7 – 7/8..