GB1140936A - Improvements in or relating to telecommunication exchanges - Google Patents

Abstract

1,140,936. Multiplex pulse code signalling. STANDARD TELEPHONES & CABLES Ltd. 23 June, 1967, No. 29101/67. Heading H4L. In a time division multiplex P.C.M. system each frame comprises n channels each having m bits one of which is used for signalling, o consecutive frames form a super frame with o Î n bits available for signalling, in each super frame some of said o x n bits are used for conveying signals which include a number of bits occurring in successive super frames and relating to the channel in which the bits occur, and a number of said o x n bits in each super frame are used as a common signal channel for signals for any of the channels. As described the system comprises 24 channels and there are 8 bits per channel of which the first bit is used for signalling or synchronizing purposes. 4 frames comprise a super frame in which in the first frame the first bits of each channel transmit signalling information which is associated with the respective channels, in the second frame the first bits are used for data transmission, in the third frame they are used as in the first frame, and in the fourth frame, the first eight of the first bits of the channels are used for order wire signalling and the remaining sixteen bits are used for synchronizing signals. Transmitting equipment.-Incoming speech signals are sampled by gates G1 &c. Fig. 1, and supplied via a common coder 1 and sync. and signal insertion device 6 to the line. Signalling on the incoming line which is associated with the channel is detected at 2 to produce an output OP1 which is supplied to device 6. Order wire signals (which are not associated in time with the corresponding channel) when received at 2 produce an output OP2 and also set a bi-stable T1 which allows the signal to be gated to a signal detector 3 which passes the signal to a store 5 via a coder 4 if a bi-stable T2 is in the reset condition indicating that the store is free. Address codes for the various lines are supplied in sequence to an address store 7 and when the detector 3 detects a potential OP2 it opens the address input gate so that the corresponding address is stored at 7. This also sets the bi-stable T2 via delay D to indicate that the store is busy, and resets T1. The signals from 5 and 7 are inserted in known manner at 6 and may require a number of super frames to complete the transmission. The sync. signals also are inserted in known manner. Bi-stable T2 is reset after the stored signal has beendealt with. Receiving equipment, Fig. 2 (not shown).- This operates in a converse manner to the transmitter and includes an order wire reception store comprising a signal store and an address store associated with signal and address decoders, the address signal gating the order wire signal on to the appropriate output line. An extraction circuit separates the various order wire and other signals and the speech signals in accordance with their time of arrival.