PURPOSE: To exclude a harmful factor without using a filter device by periodically turning on/off a transmitter and performing reception or detection only during a pause of transmission.

CONSTITUTION: A single device is so operated that the transmitter periodically radiates an electromagnetic pulse, which has a spectrum covering the resonance frequency of a label (wide band) and generates energy enough to excite the resonance circuit of the resonance label, for a short time, and the label is detected in the next pause stage with the electromagnetic wave, which the label transmits with the resonance frequency, by a receiver. Since no transmission signal exists at all and the receiver can be set to an extremely high sensitivity during a pause of transmission, the signal of the resonance label is accurately detected.