Provided is a transmitting and receiving system and method in which a transmitting and receiving device mounted on an operation system unit can process a signal received from an equipment connected to a standby system unit and a signal to be transmitted to the equipment connected to the standby system unit.A data signal and a control signal to be transmitted to a receiving device of the operation system unit are multiplexed by a parallel/serial conversion using a multiplexer. The signals are transmitted to the operation system unit as a serial received signal. The signal is demultiplexed by a serial/parallel conversion using a demultiplexer of the operation system unit. Further, a data signal and a control signal to be transmitted to the equipment connected to the standby system unit are multiplexed by a parallel/serial conversion using a multiplexer. The signals are transmitted from the operation system unit to the standby system unit as a serial signal to be transmitted. The signal is demultiplexed by a serial/parallel conversion using a demultiplexer of the standby system unit.