Abstract: A digital television chassis and a picture-in-picture module are interconnected with control microprocessor means via a three wire communications bus. Function control units in the digital chassis and in the picture-in-picture module have identical digital addresses. A logic circuit is interposed in the Ident line from the microprocessor and the Ident lines to each of the digital chassis and PIP module for selectively controlling the digital chassis and the PIP module. The microprocessor addresses the logic circuit and provides a Data signal indicating which of the digital chassis and PIP module is to be controlled.