SONET's SM-IV motorized change-over switch is designed to transfer load automatically and manually from one power source to another in 1-3 phase applications. Device monitors mains and generator control phase voltage for switching of power. In case if there is the mains control phase voltage, the device connects the load circuits to the mains inputs. If the mains control phase voltage is lost, the device comes to the mains inputs. In case if, there is the generator control phase voltage (while mains control phase voltage is absent), the device connects the load circuits to the generator inputs. If the Auto mode switch in the OFF position, user could switch the load circuit connection between mains and generator input manually..