In particular, the automatic transfer control devices 3KC are deployed everywhere where a power failure is especially critical, e.g. in hospitals, in conjunction with UPS systems, and for industrial processes. In case of a power failure, the automatic transfer control device 3KC automatically switches to a second power supply, which ensures that loads can be supplied with power at all times. The automatic transfer control device 3KC are versatility through option for switching between the power sources: system to system, system to generator or generator to generator.