Isdn network termination unit enabling to establish data link between one terminal equipment and other terminal equipments connected to the unit without use of subscriber line

Abstract From the Canadian patent

An ISDN network termination unit for connecting a user's bus line connected to a plurality of terminal equipments and a subscriber line extending from an exchanging office receives and transmits a D channel signal from one of the exchanging office and each terminal equipment to the other to thereby establish a data link between them on the D channel. The D channel signal is provided with an identifier code field. In order to establish a data link between the terminal equipments on the D channel without use of the subscriber line and the exchanging office the ISDN, network termination unit is provided with an identifier code holder for holding a predetermined identifier code and a deciding …