TechniSat TechniRouter 9/2x4 G - Handbuch (Seite 43)

43
EN
7 For Specialists: Digital Single-cable Systems according to EN 50494
7.1 How It Works
A problem in traditional satellite TV distribution systems is that they have to refer back to a
star distribution in order to provide each receiver with signals from all SAT IF banks.
Therefore, a coaxial cable must be installed from each receiver to the LNB or multi-switch,
with TWIN receivers even two. This makes it very costly to upgrade existing cable
structures to satellite TV, if not impossible. With a new method standardized according to
DIN EN 50494 it is now also possible to provide existing cable systems with satellite
signals, without limitation to the number of channels. In this case, each connected receiver
is assigned a fixed user band.
1
1
2
2
HLo
HHi
VLo
VHi
User Band
Frequency
3
3
4
4
5
5
6
6
7
7
8
8
Besides selecting the desired SAT IF bank, the LNB, or multi-switch, now also has the task
of converting the desired TV signal to the user band frequency.
Thus the name satellite channel router (SCR).
7.2 Control Signals
For controlling the router, special DiSEqC-related SCR commands are used. However, in
contrast to DiSEqC, the voltage is permanently 13V and is only raised to 18V during the
actual command.
18V
13V
Time
In coordination with the receiver’s diode-separated connection, this ensures that the
receiver sending the command has exclusive access to the common cable. As introduced
with DiSEqC, a 22kHz tone is modulated to transmit commands as digital data.
Each command contains the user band number as a kind of sender ID for the sending
receiver.