Substantially non-blocking space switching arrangement

Claim 1

An automatic telecommunication switching arrangement, which includes a switching network interconnecting inlets to the network and outlets from the network,which switching network is replicated into a plurality of switching sub-networks so arranged that any connections between an inlet and an outlet can be set up via any one of said sub-networks by contol equipment having a memory wherein: the arrangment's control equipment chooses a path between the inlet and the outlet to be connected via one of said sub-networks and sets that path up; after a said path has been set up a further search is made in the sub-networks for another path (hereinafter called a reserve path) which is usable for the same connection and the identity of that path is recorded in the control equipment's memory. if the path originally set up for a connection fails or otherwise becomes unavailable for use that path is replaced by the reserve path selected for that connection; when selecting a said reserve path note is taken of existing set up paths and of paths already reserved for possible use in the event of failure of the sub-network containing the path set up for that connection; the choice of said reserve path for a connection is so done as to ensure that the reserve path is not in the same sub-network as the connection path for which it is a reserve, if an entire switching sub-network fails all connections set up therethrough are transferred to their reserve paths; if after such a failure of an entire sub-network no reserve path exists for a connection to be set up a reserve path is selected by reserving the said replacement path; and means is provided whereby if necessary more than one such replacement may be effected.