A system is connected to a single-wire communication line to perform bidirectional communication between a master side and a slave side, and an input clock-side transistor connected between a GND level and the communication line performs switching according to an input clock. A first transistor is connected between a first potential and the communication line, a second transistor has one end connected to a second potential, and a master-side resistor is connected between the other end of the second transistor and the other end of a third transistor. A fourth transistor is connected between the communication line and a third potential equal to or higher than the first potential, and a slave-side resistor is connected between the communication line and the GND level.