4. A receiving station for use in conjunction with a transmitting station as claimed in claim 3 and based on a linear code, wherein the decision means comprise multiplier means for forming, using a parity check matrix, a syndrome value in order to reconstruct a code word from the separated word and the syndrome value.
3. A transmitting station for use in a system as claimed in claim 1 or 2, wherein the one code word identifies the transmitting station.