Abstract: A plurality of M PBXs are coupled to a plurality of N nodes forming a Distributed Transit Private Branch Exchange (PBX). The plurality of N nodes are located remotely from each other and form a wide area network. Each node is coupled to predetermined ones of the other nodes via separate links so that each node is able to communicate with all other nodes. One or more D-channel Server Modules (DSMs) are located in predetermined nodes of the plurality of N nodes. Each DSM is associated with a plurality of D channels which are each coupled to a separate interface device in the same node or different node by means of a link for receiving and transmitting signaling data to one of an associated predetermined PBX of the plurality of PBXs.