In each contactor there is a coil that operates switching and breaking, the voltage to control the coil can vary depending on the application, normally in industry is 24VDC. The contactor may also contain a PCB that controls switching on and off. Some contactors have more than one coil to reduce power consumption. Usually one more powerful to close the plug and one that draws less current to keep the plug closed. This has in modern Schaltbau contactors often been replaced by only one coil controlled by PWM signal to achieve lower power consumption and lighter contactor.