Short technical lexicon
Short technical lexicon
AC3
Audio coding MPEG 2/layer 3 - The scrambled digital sound signal for Dolby Digi-
tal. It transmits 5 sound channels and one reduced sound channel for the sub-
woofer.
DiSEqC
DiSEqC (Digital Satellite Equipment Control) is a communication system between
the Sat receiver (master) and the peripheral Sat components (slaves), such as
LNBs, multi-switch, motorised antenna systems.
This is a single master/multi-slave system, i.e. there is always only one master in
the Sat system. All activities emanate from the master.
DiSEqC components
When DiSEqC switchover matrices are cascaded, the master receiver must send
out the DiSEqC signal several times so that all DiSEqC multi-switches in the cas-
cade receive their commands.
Nowadays, DiSEqC components (slaves) must be retrocompatible, i.e. they must
also respond to the analogue switching criteria of receivers which are only
equipped with the control signals H/V and 22 kHz.
A DiSEqC switchover matrix operates with analogue switching criteria until the
DiSEqC command is received from the master. All analogue switching criteria are
then ignored.
DVB MPEG-2
DVB is the abbreviation for digital video broadcasting. DVB-S refers to the type of
transmission (S=satellite). MPEG is the abbreviation for Moving Picture Experts
Group, a working group which draws up internationally valid standards for the digi-
tal compression of video together with audio. MPEG-2 has been promoted to the
standard for the compression of digital TV signals. MPEG-2 operates at a data rate
of up to 100 MBit/s.
Eb/No ratio
The Eb/No ratio is a measure for the signal-to-noise ratio of the digital signal. This
value is not identical to the C/N value as known from analogue reception technol-
ogy. As a rule, reception is no longer possible at Eb/No levels below 5 dB.
FEC
FEC is the abbreviation for Forward Error Correction. The FEC error rate corre-
sponds to the viterbirate.
PID
The PID number (Package Identification) is an identification number for video sig-
nals and audio signals in the digital data stream of DVB MPEG-2 signals. The re-
ceiver uses the PID number to establish distinct allocation of the video and audio
data transmission. PID-PCR is the identification number for the synchronisation
signal. PID-PCR is normally identical to PID video. In the case of multi-language
channel transmissions, by means of manual entry of the audio PID, it is possible to
allocate another language to the TV broadcast. After entering the PID, the digital
receiver automatically selects audio data from the data stream identified by the PID
number and allocates these data to the video signal.
Programme package
The programme package of a digital transponder mostly contains several TV and
radio channels. Each channel package has a fixed allocation with regard to the
transponder transmit frequency, the polarisation (horizontal or vertical), the symbol
rate and the viterbirate or error rate.
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