Trunking of a t.d.m. electronic exchange with subscribers´ lines having permanently allocated multiplex channels

A t.d.m.-exchange system is described in which the subscribers´ line equipments have permanently allocated channels. If n channel multiplexes are used, the subscribers´ lines are effectively divided into n separate space-division exchanges with common registers and junctions. Existing trunking theory still applies, but with the unusual aspects that the division by n results in an aggregation of n small, or even very small, exchanges, and that the relatively high cost of the switching elements justifies greater care in trunking design to minimise the number of switching elements.