If external magnetic field(s) (external noise) is/are present, equivalent noise component(s) might be produced at both receiving coil(s) and dummy coil(s), and respective noise components from receiving coil(s) and dummy coil(s) might be made to at least partially cancel out one another at differential amplifier(s), substantially only signal component(s) due to magnetic field(s) from transmitting coil(s) being applied by way of differential amplifier(s) to comparator(s), where same is/are binarized and is/are moreover output by way of output control circuitry and respective transistor(s).