A control-target device for controlling an amount of power provided to an electrical load , the control-target device comprising: a memory for storing a device type associated with the control-target device; a communications circuit ; and a control circuit , wherein the control circuit is characterised in that it is configured to: receive, via the communications circuit , a discovery message from a user device , wherein the discovery message comprises an indication of a type of control-target device ; compare the type of control-target device indicated in the discovery message with the device type associated with the control-target device ; send, via the communications circuit , a discovery response to the discovery message when the device type is the same as the type of control-target device indicated in the discovery message, wherein the discovery response indicates whether the control-target device is within an established range of the user device ; receive, via the communications circuit , an association message from the user device , wherein the association message comprises identification information of a control-source device; and store, in the memory , the identification information of the control-source device, wherein the identification information of the control-source device enables the control-target device to recognize digital messages from the control-source device. a memory for storing a device type associated with the control-target device; a communications circuit ; and a control circuit , wherein the control circuit is characterised in that it is configured to: receive, via the communications circuit , a discovery message from a user device , wherein the discovery message comprises an indication of a type of control-target device ; compare the type of control-target device indicated in the discovery message with the device type associated with the control-target device ; send, via the communications circuit , a discovery response to the discovery message when the device type is the same as the type of control-target device indicated in the discovery message, wherein the discovery response indicates whether the control-target device is within an established range of the user device ; receive, via the communications circuit , an association message from the user device , wherein the association message comprises identification information of a control-source device; and store, in the memory , the identification information of the control-source device, wherein the identification information of the control-source device enables the control-target device to recognize digital messages from the control-source device. receive, via the communications circuit , a discovery message from a user device , wherein the discovery message comprises an indication of a type of control-target device ; compare the type of control-target device indicated in the discovery message with the device type associated with the control-target device ; send, via the communications circuit , a discovery response to the discovery message when the device type is the same as the type of control-target device indicated in the discovery message, wherein the discovery response indicates whether the control-target device is within an established range of the user device ; receive, via the communications circuit , an association message from the user device , wherein the association message comprises identification information of a control-source device; and store, in the memory , the identification information of the control-source device, wherein the identification information of the control-source device enables the control-target device to recognize digital messages from the control-source device. <EOS>