Modular self-routing pcm switching network for distributed-control

Abstract

An automatic exchange of a telephone system comprises a PCM switching network with a plurality of cascaded stages for establishing temporal and spatial connections between incoming channels on input lines of the first stage and outgoing channels on output lines of the last stage in response to commands from external controllers dialoguing with internal controllers of the network. Pairs of switching matrices forming part of nonadjacent stages are combined ito modular switching units each provided with its own internal controller. Routing instructions are transmitted from an external controller to a first internal controller which selects a signal path through the matrices of its own switching unit and informs a second internal controller of that selection whereupon the latter extends the path through an adjoining switching unit, and so on until the connection is completed. Each matrix is provided with a data store which is asynchronously loadable from the associated internal controller with a routing instruction to be synchronously forwarded, in a special time slot dedicated to intercontroller dialoguing in a PCM group to which the instruction pertains, to the data store of a coacting matrix in the next stage for asynchronous retransmission to the controller thereof; each data store may be paired with a respective series/parallel converter coupling it to the associated matrix for serially loading that store in any PCM frame with the contents of the dedicated channels of concurrently arriving PCM groups and feeding stored instruction words in parallel to the output lines of the matrix during a predetermined time slot of each frame. The internal controllers also perform diagnostic operations by comparing bytes extracted from an established signal path at locations upstream and downstream of a matrix.