Provided is a system for supplying a power from a sink device to a source device. Not only the source device but also a cable or a repeater device to be connected thereto has compatibility in power supply. A physical address obtained from information of an EDID memory forms a base of CEC message exchange, but a physical address of the cable or repeater device is overlapped with the source device or unknown. The cable or a repeater device uses changes the type of a message while using the same physical address as the source device or use such a message having the physical address information of the source device is described in a parameter of the message using the unknown physical address. The message having a supply or reception current for each device described therein is exchanged with the sink device or the source device to adjust current reception.