Relays and contactors are similar in design and function, differing mainly in the power range, which largely determines the applications. Relays are low-cost electromagnetic switches with two switching positions that are established in a variety of designs. Typical are small relays, solid state relays and heavy current relays. An important area of application is passenger cars, which are equipped with petrol pump, indicator and glow time relays, for example. In addition, relays are used in a wide range of industries. Electromagnetic switches consist of a coil, armature and normally open contacts. Functionally, the control circuit generates a ferromagnetic coil field and attracts the armature. The change in inclination of the armature closes the working contacts and current flows in the working circuit to the connected consumers. Due to the amplifier function, a small current is sufficient to control the working circuit with a large current. Voltage and current peaks are not critical for relays. Relay alternatives are semiconductors and semiconductor circuits. Contactors, also called switching contactors, are electrically operated switches that can be divided into power and auxiliary contactors. Auxiliary contactors are used, for example, in a self-holding circuit to switch the power contactor on and off. Monitoring tasks can also be performed by contactor relays. An important difference between contactors and relays are the higher loads, which start at 500 watts and increase up to several hundred kW depending on the model. Contactors have two switching positions (open, closed) and are used for switching circuits. Accordingly, control applications, for example of 3-phase motors, pumps, heating and air conditioning systems and building automation are typical.