Fundamental parts of electrical utilization and distribution systems are associated circuitry and Motor control gear. An electrical switching device is a contactor like an outside ac unit contactor. For switching on and off in an electrical circuit, it is used. Between a relay and the contactor, there is a basic difference and it is a special type of relay.

In applications where higher current carrying capacity is involved, the contactor is mostly used while for lower current applications, the relays are used. Contactors can be field-mounted easily and are compact. Operating power to the load is provided by the contacts and whenever the contactor coil is powered, they are mostly normally open. With electric motors, Contactors are popularly used.

Various types of contactors are there, and their own sets of capabilities, applications and features are present in the various types. Ranging from voltage from 25V to thousands of volts DC and a few amperes to thousands, a vast range of currents can be taken over by the contactors. Furthermore from small hand-held dimensions to large sizes, these devices come in various sizes measuring up to a yard or a meter on one side.