EN 50494:2007 – Satellite signal distribution over a single coaxial cable in single dwelling installations

5 SCIF control signals
5.1 DC levels
In a single coaxial cable distribution system, all controls issued by the receivers (demodulators) are done according to the DiSEqC format.
The single coaxial cable distribution system is not backwards compatible with the former 13/18 V control associated with a continuous 22 kHz tone. The single coaxial cable distribution system is also not backwards compatible with the tone burst signalling.
In single coaxial cable distribution systems, the signal-sending receiver generates a high DC level upon which the DiSEqC control signals are added. After sending the DiSEqC control signal the receiver returns to an idle mode in which it generates a low DC level onto the single cable distribution system (refer to Figure 6). With reference to EN 61319-1, the low and high DC level shall have the following limits on the signal-sending- receiver side:
– LOW _DC value: 12,5 V to 14 V
– HIGH_ DC value: 17 V to 19 V
The delays (td & ta) shall have the following limits:
– td min > 4 ms and td max < 22 ms – ta min > 2 ms and ta max < 60 ms The hardware of the communication bus has to be realized according to the DiSEqC bus functional specification. Some additional care shall be taken to ensure an appropriate impedance of the installation during the DiSEqC sequences. In Annex A implementations are suggested. 5.2 Method of the data bit signalling DiSEqC uses base-band timings of 500 µs (+/- 100 µs) for a one-third-bit PWK coded signal on a nominal 22 kHz (+/- 4 kHz) carrier. See DiSEqC bus functional specification and EN 61319/1996/A11:1999. Figure 7 shows the 22 KHz time envelop for each bit transmitted, with nominally 22 cycles for a bit “0” and 11 cycles for a bit “1”. 5.3 Structure of the DiSEqC message in the single coaxial cable system The structure of the message sent by the receiver to the SCIF is described in Figure 8. Each message contains 5 bytes of 8 data bits each, an odd parity bit is added to each byte. A byte has a typical duration of 13,5 ms; the 5 bytes message lasts 67,5 ms. EN 50494:2007 – Satellite signal distribution over a single coaxial cable in single dwelling installations