PC-FJKG user demarcation switch controller (commonly known as the "watchdog" )is an automation control device integrated functions of  shortage ground fault detection, relay protection control, communication (after communication modules were configured ) and other functions, based on the microprocessor core, which is suitable to be installed at the T-type wiring place of the 10KV distribution line user, or branch lines and end of the line according to load requirements . After the controller was installed and put into operation, it can control the boundary breaker, quickly and automatically remove single-phase ground fault of the user, and short troubles between phases of automatic isolated user. The super capacitor is a backup power supply,which can provide an open and close switch operation for the controller when the line power failing.