Abstract: A proximity switch has at least three Hall effect magnetic field sensitive transducers mounted in a transducer housing and has at least two magnets mounted in a magnet housing. The transucers produce logic signals, and a logic circuit responsive to these logic signals activates an electrical switch only when the magnets are in a proper position relative to the transducers. The electrical switch may be used to control a machine, and the machine is not activated until the proximity switch is activated.

Abstract: An electric circuit for energizing an intrinsically safe pilot light having a cluster of light emitting diodes arranged in a pattern and visible through a lense cap located in a hazardous area. The pilot light has terminals connected through the circuit that includes a rectifying bridge and a current regulator to the diodes to optimize the light output of the diodes and make the pilot light insensitive to the polarity of an A.C. or D.C. intrinsically safe electrical supply to the pilot light and limiting the current to the diodes to a constant value in event one or more of the diodes is destroyed or shorted. A pair of printed circuit boards are spaced by a plurality of conductive supports with one of the boards mounted on a base of the pilot light and carrying the rectifier and current limiting components which are connected to the terminals.