Abstract: An interactive audio/visual demonstration system for connection to a telephone system, comprising an audio/visual unit connected to an interface circuit. The interface circuit decodes DTMF tones received from the audio/visual unit and in response causes implementation of one or more special features in the telephone system. The interface circuit is preferably connected to an audio track of a video tape recorder, and to the telephone system, such as a PABX, in order to implement a highly interactive video tape presentation in response to a video tape being played on the video tape recorder. The interface circuit is of simple construction and hence durable and inexpensive.