Abstract: Port networks (PN 101-103) of a switching system such as a distributed PBX are remoted from and interconnected with each other by an ATM network (100). Each port network includes a port network connectivity (PNC) circuit (113-114) that interfaces it to the ATM network. Only one of the port networks (101) has a system processing element (SPE 111), which controls all of the port networks. Commands issued by the SPE and needed by the ATM network to establish virtual circuits between the port networks are translated (FIG. 2) by a PNC circuit (113) into ATM signaling cells. Commands issued by the SPE and not needed by the ATM network are encapsulated (FIGS. 2 and 3) as payload into ATM traffic cells by the PNC circuit and are sent to destination processor networks through the virtual circuits. At a destination processor network, the encapsulated commands are retrieved (FIGS. 2 and 3) and used for local control.