PURPOSE: To allow the receiver to be usable for both an electromagnetic receiver and a piezoelectric receiver.

CONSTITUTION: A drive circuit for an electromagnetic receiver and drive circuit for a piezoelectric receiver are provided in parallel and a receiver discrimination circuit 34 discriminating whether a connected receiver is an electromagnetic receiver or a piezoelectric receiver is provided. When the circuit 34 discriminates that the electromagnetic receiver 26 is connected, a drive circuit selection circuit 35 selects the drive circuit for the electromagnetic receiver to form a reception circuit and when the piezoelectric receiver 26 is connected, the drive circuit selection circuit 35 selects the drive circuit for the piezoelectric receiver to form the reception circuit.