may be generated from the sequences of symbols given in table 1 the first sequence of each block being preceded by the symbols a i set to zero constant phase and followed by the information symbols that are unknown a priori whereas the second sequence of each frame is preceded by the symbols that are unknown a priori and followed by the symbols a i set to zero in the receiver illustrated in fig8 the means 11 for detecting synchronisation patterns conduct a search in parallel of the patterns associated with the above sequences depending on the sequence identified signalling information z the detection means 11 issue a command to the demodulator 12 which may operate in a conventional manner using the viterbi algorithm with a simple demodulation trellis 60 where modulation on the tch channel is non coded or with a supertrellis 61 integrating the modulation and convolutional coding states in order to obtain the gain of the coded modulation on the tch or facch the demultiplexer 62 which directs the flow of symbols output by the demodulator 12 either to the units 63 processing the traffic channel tch or to the units 64 processing the signalling channel facch the units 63 processing the traffic channel tch to indicate what the transmission rate is on this channel the radio communication system incorporating the transmitters illustrated in fig7 and the receivers illustrated in fig8 have the advantage of enabling.