Abstract: A switch system for an industrial machine is described which combines both optical and capacitance switches in a switch assembly. A photo-optical switch is positioned in each assembly to provide an output signal upon the introduction of a human hand into an opening formed therein, and a capacitance sensitive touch plate switch is positioned within the opening to provide an output signal upon contact by a human hand. Circuitry responds to the substantially simultaneous activation of both the optical and capacitance switches within the switch assembly and produces an output signal. Typically two of such switch assemblies are used to control power to an industrial machine.

Abstract: The present invention employs a plurality of spaced light beam sources and corresponding photodetectors to form a light screen. A programmed microprocessor and memory circuitry senses the photodetector output and stores information on the position of an allowed obstruction. During operation of the equipment, the microprocessor repeatedly senses the photodetector output to determine which channels are blocked. When dangerous changes occur in the size, position or presence of an obstruction, the system alerts the operator or stops the equipment.

Abstract: A hand operated photoelectric switch having a channel providing an interrupt area for an operator's hand to pass into the path of an infrared light beam passing from a light emitting diode to a phototransistor sensor. Said housing further including circuitry for operating a mechanical relay to be activated for the operation of electrical machinery. A monitoring circuit is provided to monitor the light emitting diode and a driver transistor for the mechanical relay whereby to detect the failure of either one and disable the circuit from accidentally providing contant closure of the mechanical relay.