Abstract: A microcomputer integrates a Digital Subscriber Terminal (DST) adapted to an Integrated Services Digital Network (ISDN). In addition to the electronic circuit boards that ensure all the normal data processing and management functions (central processing unit, input/output circuits, ROM and RAM circuits), the microcomputer is equipped with an additional set of circuit boards for interfacing with an ISDN system, so as to constitute a microcomputer-contained DST for an ISDN. The management and switching of data concerning the ISDN system are provided by the additional set of circuits, so that the DST function is achieved without calling on the resources of the microcomputer's central processing unit. In this way, the essential telephone switching function is obtained without calling on the PC's central processing unit, while the integration of the DST within the PC makes it possible to benefit from the computer's data processing functions with a minimum amount of equipment for a maximum number of functions.