Communications system comprising an ISDN terminal equipment connection for different ISDN interfaces in an ISDN switching equipment network

A communications system comprising, an integrated service digital network switching equipment having two-wire, ISDN transmission (U) interfaces and four-wire, standardized ISDN bus (S) interfaces, and having ISDN terminal equipment which are respectively connected either to an ISDN transmission interface through an ISDN transmission terminating equipment realizing a layer 1-functions of the OSI reference model for an integrated transmission procedure or to one of the ISDN bus interfaces through an ISDN terminating equipment realizing a layer 1-function of the OSI reference model for an ISDN bus interface, whereby, through a control input, an ISDN bus terminating equipment is drivable either into an operating mode realizing the layer 1-function at the side of the switching equipment or into an operating mode realizing the layer 1-function at the side of the ISDN terminal equipment and, at the side of the switching equipment, a current source is provided for the remote power supply of the ISDN terminal equipment connected through a central office line which is coupled directly to the two lines of the two-wire interface or to a phantom circuit of the four-wire ISDN bus interface, characterized in that an ISDN transmission terminating equipment (U.sub.o E) and an ISDN bus terminating equipment (S.sub.o E) are provided for an ISDN terminal equipment;

• the current type of connection of the current source at an exchange is identified at the respective interfaces by a detector means (DE) which is connected to the ISDN terminal equipment, and which is also connected to switch means (SM) so as to connect either the ISDN bus terminating equipment (S.sub.o E) or the transmission terminating equipment (U.sub.o E) to the respective ISDN interface.