The Model 857B card frame package will allow mounting of up to 10 audio modules, and is designed for use with the external power supply Model 66708. The external power supply has sufficient current rating to allow multiple power amplifiers to be mounted within a single card frame, and/or to power multiple card frames in larger systems. Busing, and connections are similar to the Model 858B package. In order to accomodate the wide variety of grounding schemes encountered in large audio systems, both card frame packages incorporate a ground-lift switch. The switch allows the INTEGRA III SYSTEM to interface with any other equipment grounding requirement.