Patent ID: 8639841

Claim:
A system, comprising: a first interface circuit including: a first transmitter, including an amplifier, configured to transmit a first signal as a first differential signal to a second interface circuit through a transmission line; and a second transmitter, including a first adder, configured to transmit a second signal, being multiplexed to the transmission line, as a common-mode signal to the second interface circuit, the first adder being configured to receive the first differential signal from the amplifier and output the second signal for transmission; a first communication circuit that communicates with the second interface circuit via a pair of differential transmission lines included in the transmission line, wherein the first communication circuit includes a circuit for biasing the transmission line to a first voltage level to indicate a connection to the transmission line, thereby notifying the second interface circuit of a connection status of its own device by at least one of direct current bias potentials of the pair of differential transmission lines; the second interface circuit including: a first receiver configured to extract the first signal from the first differential signal received from the first interface circuit through the transmission line, the first receiver comprising a second adder configured to add the extracted first signal to an inverted signal; a second receiver configured to extract the second signal from the common-mode signal received from the first interface circuit through the transmission line, the second receiver comprising a third adder configured to extract the common-mode signal by adding a second differential signal and a third differential signal; and a second communication circuit that communicates with the first interface circuit via the pair of differential transmission lines included in the transmission line, wherein the second communication circuit receives a notification of the connection status from the first interface circuit by at least one of the direct current bias potentials of the pair of differential transmission lines.