Abstract: An automatic telephone system enabling subscribers access to more than one network (3,4). The subscriber's line (2) accesses the networks (3,4) via a highway providing at least two traffic channels (B) and one signalling channel (D). The signalling channel (D) conveys call setting and other signalling for calls set up via any traffic channel (B). Access of a particular traffic signal channel to a particular network is provided by an intelligent multiplexer/concentrater (1) in response to a network identifier carried by the signalling channel, for example an appropriate value of a SAPI (Service Access Point Identifier) in the case of an ISDN I-Series signalling system.