Abstract: A telephone exchange, now often called a switch, includes a switching network of the space division type which switches PCM highways, and includes a number of sub-networks (SEG1, SEG2 . . . SEGN) each of which is a plural (e.g. three) stage array. When a call is to be set up it is set up via one of these sub-networks, and a reserve path chosen for it through a different sub-network. The identity of this reserve path is noted in memory for use if the path via which the connection is actually set up fails. If that happens the call switched to the reserve path. This facility can also be used for "block transfers" of all calls in a sub-network, e.g. when the latter is taken out of service for maintenance. In one embodiment in which three stages are used, part at least of the middle stage is common to all sub-networks. Such an apparently large amount of switching corss-points is not too "cost ineffective" since the switching sub-networks are made up of relatively cheap VLSI units. Since the physical paths are e.g.

Abstract: In a fully digital telephone switching system, a digital switch may serve a number of PCM sub systems each having separate forward and reverse highways and each serving a number of subscribers' lines. The highways are grouped in blocks of eight, from which intelligence is received in serial byte-interleaved form and converted by serial-parallel converters to parallel byte-interleaved form. While in this form they are switched to other channels and applied to a super-multiplexer which they leave in parallel byte-interleaved form from which they are restored by another converter to serial byte-interleaved form for application to the switch's outputs. For the reverse channel the arrangement is the reverse of the above, i.e. serial-parallel conversion, switching and parallel-serial conversion to the line multiplex highways. For local calls a loop-back connection is provided via a fixed delay of half a frame time. Thus, if the outputs fail, the arrangement can still handle local calls.

Abstract: A digital switching arrangement for use in a telecommunications exchange handling channels of digital information in time division multiplex form. The digital switching arrangement being particularly suited for use in stored program processor controller environments. The arrangement comprises a digital switching network and a control equipment. The control equipment includes an input queue and an output queue each arranged to store processor input and output messages respectively. The control arrangement is arranged to asynchronously process each output message to process switching network path connections and to generate in the input queue an input message indicative of the actions performed. Each output message includes switching network identification information indicative only of the identities of the incoming and outgoing exchange highways and channels to be involved in the switching network path to be processed.

Abstract: Queuing of interexchange messages in a multi-exchange digital telecommunication network is provided using a dynamic store into cells of which the messages are placed. A subsidiary control store has a cell for each cell of the message store and each of these cells contains a control word which contains the status-busy/free of its message cell, plus details of the message including the user for which it is stored when the cell is busy. These details include message priorities, so that queues of messages awaiting attention can be assembled in the store.

Abstract: A digital switching telecommunications exchange handling pulse code modulated information samples in time division multiplex form on incoming and outgoing junctions. The exchange includes a receive interface for each incoming junction and a transmit interface for each outgoing junction and a pair of identical time division multiplex switching networks providing interconnection paths between any incoming junction channel and any outgoing junction channel. Under non-fault conditions exchange calls use indentical paths in each network and the transmit interfaces include error checking and comparison arrangements for each pair of information samples received under fault conditions the transmit interfaces can be arranged to select the non-faulty sample on a per channel basis or can be biased to select one network exclusively.