Abstract: A TDM switching system for providing selected connections between large numbers of lines and trunks and which may combine, in an integrated system, several TDM switching systems which are adapted to handle smaller numbers of lines and trunks so as to expand the capacity of such smaller TDM systems. The system has a distributed, modular architecture in which the lines and trunks are arranged in a plurality of domains. The domains each have a link controller which links the domains to interdomain PCM highways. The domains each include, as the members thereof, a plurality of devices.