GB1263007A - Improvements in or relating to pcm time-division multiplex exchange systems - Google Patents

Abstract

1,263,007. Automatic exchange systems. SIEMENS A.G. 3 March, 1970 [4 March, 1969], No. 10003/70. Heading H4K. In a PCM, TDM exchange utilizing one time slot for transmitting signalling data in respect of connections taking place in the other time slots, each data signal is accompanied by a designation signal for identifying the time slot to which the data signal relates. A number of time slots may be grouped under a common designation signal, the data signals being related to the time slots by virtue of their order within the group. As shown, an address generator AG<SP>1</SP> supplies the address of a group of subscriber lines VS<SP>1</SP> during a frame period. The conditions of the a, o wires of each line in the group are sampled and the results stored in parallel in shift register SR<SP>1</SP>. The conditions may be in respect of dialling signals or clearing signals as described. The address of the group is also entered into the shift register. Thereafter during the time slot, e.g. p16, devoted to data signalling the contents of the register are serially shifted from the register on to the highway PCM. An obvious system for decoding and distributing the data signals at the receiving end of the highway is depicted in Fig. 2 (not shown). The continuous transmission of the time data during successive time slots of the data channel may be effectively interrupted, if one of the lines changes its state, by transmitting the change data together with the identity of the line (or rather, the identity of the time slot utilized by the line) producing the change during the next time slot in place of the line data originally intended for this slot. The original D.C. line signals may be reconstructed (e.g. with relays) at the TDM exchange so as to be compatible for subsequent signalling to an electromechanical exchange.