Abstract: An audio receiver or other electronic device having a number of controllable functions is provided with control apparatus in which mechanical parts have been substantially eliminated. An electrically controllable device is provided to control each function. Memory registers provide inputs to the electrically controllable devices. The controllable functions may be on-off, as for a particular signal source, or may be variable, as for volume, tuning and tone in a receiver. Input controls include a single level control for adjusting the levels of all of the variable functions, and switches to select the function to be adjusted. Control means such as a microprocessor scans the switches and level control for changes in level and/or functions selected and updates the memory registers accordingly. A display is provided of selected functions and level.

Abstract: A modular switching system including a plurality of switch modules connected in cascade. Each module includes a portion of a signal bus, terminals for connection of an external device, switch means for connecting the external device to the signal bus and an addressable logic circuit. An external device can be connected to the signal bus by providing to the logic circuit cascade a number of address pulses corresponding to the position in the cascade of the selected external device. By providing a number of such cascades an entire system, for example an audio system, can be formed. The system can be expanded simply by connecting additional switch modules to each or any cascade and an external device connected thereto is automatically addressable according to its position in the cascade.