Abstract: PCM telephone transmission apparatus and particularly the use of several ra binary positions in a multiplex frame. These positions are used in one or several units auxiliary to the main unit which processes PCM telephone signals. The auxiliary unit(s) include(s) a signalling time base identical to the signalling time base of the main unit. The counting signals for this auxiliary time base are at a lower rate than the counting signals of the main unit, but they are applied in such a way that a part of the auxiliary time base counts at the same rate as the corresponding part of the time base in the main unit. This structure enables an evolutive use of the extra bits without modification of the main unit.

Abstract: The invention comes within the field of digital transmission and concerns e synchronization of two bit trains in relation to the beginning of a frame. According to the invention, one of the trains crosses a memory of the FIFO type, whose writing speed corresponds to the frequency of that train and whose reading is controlled by a detector of the locking word in that frame and by a signal indicating the synchronization of the two trains. Application: digital PCM terminals comprising thirty telephone channels.

Abstract: A main pulse train at a main frequency and at least two derived pulse tra at submultiples of the main frequency are transmitted over a transmission path, from a transmitter to a receiver, in the form of pulses of alternating polarity. A first one of the derived pulse trains is transmitted as a single violation of bipolarity in the main pulse train while a second one of the derived pulse trains is transmitted as two successive violations of bipolarity in the main pulse train. The system is applicable to multiple synchronization (bit, frame etc . . . ) in a PCM digital transmission or switching system.