Pcm switching network with surplus capacity

Abstract

A network for selectively switching channels from n incoming PCM links to as many outgoing PCM links comprises two sections of a receiving-side stage with n input terminals each, connected in parallel to respective incoming links, and with m output terminals working into an intermediate stage with 2m input terminals and as many output terminals. The latter are connected to respective input terminals of two sections of a transmitting-side stage with n output terminals each; homologous output terminals of the two transmitting-side sections are alternatively connectable to respective channels of n outgoing PCM links by means of multiplexers which are switched by a logic unit under the control of a processor also detecting possible malfunctions in any section. Each stage consists of a multiplicity of temporal or spatial switching matrices. With m lying between n/2 and n, and with all matrices operating normally, the logic unit routes about half the incoming channels through each receiving-side section and each transmitting-side section; the matrices of the intermediate stage provide a plurality of alternate paths between any receiving-side matrix and any transmitting-side matrix. When a receiving-side or transmitting side matrix fails, the routes established therethrough are transferred to its counterpart in the other section of the respective stage; failure of an intermediate matrix results in a redistribution of its routes through the remaining matrices of this stage.