Inductive Proximity Switches are solid state switching devices based on Eddy Current Loss Principle. An alternating electromagnetic Field is developed at the sensing face of the proximity switch. When any metallic object enters this field the eddy current increase. The amplitude of the oscillations of electro magnetic field is consequently reduced. This reduction in amplitude is processed and an output stage is switched on or off. For DC switches this output stage is either a PNP or NPN transistor and For AC switches it is a Thyristor.