Abstract: A multidrop network for effecting communications between a master site and a plurality of remote slave sites employs a multiport multiplexer at the master site and at slave sites, for interfacing multiple ports to a single telephone communication link. At the master site multiple/diverse types of data/signal processing equipments are coupled to respective ports of a master communications multiplexer or concentrator. Under internal processor control the master concentrator interfaces one of its input ports to an associated communications modem by way of which messages are exchanged over the telephone link. That input port of the master concentrator which is interfaced to its associated modem establishes a corresponding destination port of each remote concentrator that is coupled to a respective drop distributed along the telephone link.