CIRCUIT FOR SUPERPOSING AND TRANSMITTING AND RECEIVING TWO-WAY DATA ON VIDEO SIGNAL

摘要

PROBLEM TO BE SOLVED: To provide a two-way data superposing and transmitting and receiving circuit on a video signal at a low cost with downsizing suitable even for a digital LSI that can transmit a voltage amplitude of data superposed and transmitted in a reverse direction in excess of a maximum level of the video signal and maintain a specified value for the maximum level of the video signal transmitted in a forward direction. SOLUTION: A switch circuit A22 of a reception section 4 is closed to connect a divide resistor 20 to ground while a timing generating circuit B23 outputs a reverse direction data super posing period control signal 104. A voltage of a data output from a data output circuit 27 is divided by minimizing the resistance of a data output resistor A21 and properly selecting a ratio of the resistance of a series resistor 19 to the resistance of the divide resistor 20 so that a transmission section output video signal 102 can superpose reverse direction data with a high amplitude such as 4 V to 5 V on the video signal and an amplifier clamp circuit 10 in the reception section 4 can suppress the amplitude within 1.0 Vpp at its input terminal.