Abstract: The technical field of the invention generally concerns systems for audiovisual teleservices using digital telecommunication services such as Integrated Services Digital Network ("ISDN") communications. In the preferred embodiment, an interface subsystem (100) includes an ISDN interface circuit (130) for concurrently exchanging audiovisual information with an ISDN access. The interface subsystem (100) also includes a host computer interface circuit (144)for exchanging video, audio, high-speed, a low-speed data with a host digital computer. A computer program executed by a digital signal processing circuit (122) implements CCITT's H.221 and H.242 Recommendations for audiovisual teleservices, and provides a computer program at the application layer (44) of the OSI model that is executed by the host digital computer with an interface by which it can exchange video, audio, high-speed, and low-speed data with another compatible terminal using digital telecommunications.