Patent ID: 8898727

Claim:
A transmission device comprising: a HDMI transmission unit configured to transmit video signals from the transmission device to an external device in accordance with an HDMI standard via one or more channels interconnected to an HDMI terminal; a high-speed data line interface configured to communicate with said external device via a pair of differential transmission paths interconnected to said HDMI terminal; a processor configured to transmit first function information to said external device for notifying said external device that said transmission device includes said high-speed data line interface that supports transmission of at least one of an Ethernet signal and a digital audio signal, said first function information being transmitted via a control data line interconnected to said HDMI terminal; the processor being further configured to receive second function information via the control data line from said external device in response to the first function information, said second function information in turn indicating that said external device also includes a respective high-speed data line interface configured to communicate the at least one of an Ethernet signal and a digital audio signal with said high-speed data line interface of the transmission device via the pair of differential transmission paths interconnected with said HDMI terminal; the processor being further configured to cause communication information indicating a communication shutoff state with said external device to be transmitted to said external device via the control data line interconnected to said HDMI terminal, and wherein the pair of differential transmission paths include a reserve line and an HPD line interconnected to the HDMI terminal, and at least one of said pair of differential transmission paths further includes a function for providing a connection state of said external device using a DC bias potential.