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 (HPD) 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 (HPD) 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 (HPD) 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 . <EOS>