A transmission method for use in a transmitter, an HDMI sending unit of the transmitter unidirectionally transmitting, to a receiver using a first differential signal, pixel data of an uncompressed image of one screen during an effective video period representing a period from one vertical synchronization signal to the next vertical synchronization signal excluding horizontal blanking intervals and a vertical blanking interval, the method comprising the steps of: transmitting by Report Physical Address of CEC control protocol, to the receiver, a notification indicating that the physical address of the transmitter designates a CEC-compliant device having a specified logical address, said specified logical address being indicative of a device type of the transmitter; characterized in that the method further comprises: transmitting by a LAN sending circuit of said transmitter, to the receiver, a second differential signal representing transmission data different from the pixel data via differential transmission lines formed from a pair consisting of the reserved line and the hot plug detect line of an HDMI cable; receiving, by a LAN signal receiving unit of the transmitter, connected to the LAN sending circuit, an added signal comprising said second differential signal added to a third differential signal transmitted from the receiver via the reserved line and the HPD line of the HDMI cable; and subtracting, by a subtracting circuit of the transmitter, said transmission data represented by the second differential signal from the signal received by the LAN signal receiving unit. transmitting by Report Physical Address of CEC control protocol, to the receiver, a notification indicating that the physical address of the transmitter designates a CEC-compliant device having a specified logical address, said specified logical address being indicative of a device type of the transmitter; characterized in that the method further comprises: transmitting by a LAN sending circuit of said transmitter, to the receiver, a second differential signal representing transmission data different from the pixel data via differential transmission lines formed from a pair consisting of the reserved line and the hot plug detect line of an HDMI cable; receiving, by a LAN signal receiving unit of the transmitter, connected to the LAN sending circuit, an added signal comprising said second differential signal added to a third differential signal transmitted from the receiver via the reserved line and the HPD line of the HDMI cable; and subtracting, by a subtracting circuit of the transmitter, said transmission data represented by the second differential signal from the signal received by the LAN signal receiving unit. transmitting by a LAN sending circuit of said transmitter, to the receiver, a second differential signal representing transmission data different from the pixel data via differential transmission lines formed from a pair consisting of the reserved line and the hot plug detect line of an HDMI cable; receiving, by a LAN signal receiving unit of the transmitter, connected to the LAN sending circuit, an added signal comprising said second differential signal added to a third differential signal transmitted from the receiver via the reserved line and the HPD line of the HDMI cable; and subtracting, by a subtracting circuit of the transmitter, said transmission data represented by the second differential signal from the signal received by the LAN signal receiving unit.