Short technical lexicon
Short technical lexicon
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 switching matrices are cascaded, the master receiver
must send out the DiSEqC signal several times so that all DiSEqC
multi-switches in the cascade receive their commands.
Nowadays, DiSEqC components (slaves) must be retro-compatible,
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 digital 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 technology. 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 corresponds to the viterbirate.
PID
The PID number (Package Identification) is an identification number
for video signals and audio signals in the digital data stream of DVB
MPEG-2 signals. The receiver 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.
Symbol rate
The symbol rate describes the amount of data transmitted per second.
The symbol rate is measured in MSymbols/s and is equal to the
number of symbols that are received per second.
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