After configuring wireless connection, the wireless communication establishment unit 102 in the adapter 100 establishes wireless communication with the access point 50 located at house at S12. It should be noted that, in this embodiment, after finishing configuring wireless connection of the registered adapter 100, the user can check the content of the configured wireless connection on a network setting confirmation screen illustrated in FIG. 8A. As illustrated in FIG. 8A, on the network setting confirmation screen, names, serial numbers, IP addresses, and MAC addresses of the adapters 100 that establish wireless communication with the access point 50 are listed. In response to selecting a “detailed setting” key displayed on the list by user operation, the network setting confirmation screen transitions to a network detailed setting screen illustrated in FIG. 8B. The network detailed setting screen accepts detailed setting for the network configuration of the adapter 100 from a user input.

Next, the bases 11 of the registered adapters 100 are each located at registered areas by user operation (S13). More specifically, after removing the light bulb 30 from the socket laid out at the registered location, the base 11 of the adapter 100 whose installed location is registered is screwed into the lamp holder of the socket 20, and the base of the removed light bulb 30 is screwed into the lamp holder 13 of the holder unit 12 of the adapter 100. As a result, the socket 20 is electrically connected to the light bulb 30.