receiving a first PLC signal at a switch of a first switch control apparatus, the first switch control apparatus comprising the switch and a coupling circuit, the coupling circuit being connected in parallel to inlet and outlet ends of the switch;

transmitting a first PLC signal through the coupling circuit to a gateway device when the switch is open or transmitting a second PLC signal to the gateway device using the switch when the switch is closed;

receiving a third PLC signal in a second switch control apparatus, the second switch control apparatus comprising a second switch, a second coupling circuit connected in parallel to inlet and outlet ends of the second switch, and a PLC module connected to an inlet end of the second coupling circuit;

sending a third PLC signal to the gateway device using the PLC module, the third PLC signal comprising a first address identifier corresponding to the first switch control apparatus;

receiving a first broadcast message broadcast by the second switch control apparatus, the first broadcast message comprising power-off information;

sending a report message to the gateway device in a unicast manner, the report message carrying a second address identifier corresponding to the second switch control apparatus; and

broadcasting a first reply message when an acknowledgment message returned by the gateway device is received, the acknowledgment message carrying the second address identifier, and the reply message carrying the second address identifier.