Patent ID: 8643423

Claim:
A communication circuit for communicating between a first equipment and a second equipment, comprising: a conversion circuit that is configured to convert an input signal to a first intermediate signal, and convert a second intermediate signal to an output signal; an input port that is configured to input said input signal from a control unit in said first equipment to said conversion circuit; an output port that is configured to output said output signal from said conversion circuit to said control unit; and a communication port that is configured to input said second intermediate signal from said second equipment through a communication line to said conversion circuit, and output said first intermediate signal from said conversion circuit through said communication line to said second equipment, wherein a voltage of said first intermediate signal is determined based on a voltage of a power source if said first intermediate signal is logic high, and a voltage of said second intermediate signal is determined based on said voltage of said power source if said second intermediate signal is logic high.