Patent ID: 7801483

Claim:
A receiver that receives an induced electric field from a transmitter or a transceiver which modulates information to be transmitted with an alternating-current signal having a predetermined frequency and includes a variable reactance section that produces resonance with a stray capacitance between a circuit ground of the transmitter or the transceiver that strays from an earth ground and the earth ground and an impedance between an electric field transmission medium and the earth ground, in an electric field communication system that induces an electric field based on the information to be transmitted in the electric field transmission medium, and uses the induced electric field to transmit the information and that, on the other hand, receives the electric field induced in the electric field transmission medium based on the information to be received, thereby performing communication, the receiver comprising: an electrode that transmits/receives the electric field to/from the electric field transmission medium; a detection signal source that applies a detection signal to the electrode; and a detecting section that detects the detection signal, further detects, based on an amplitude of the detection signal, a resonant state of the variable reactance section of the transmitter or the transceiver held by the electric field transmission medium near the electrode, an impedance between the electric field transmission medium and the earth ground, and the stray capacitance between the ground of the transmitter or the transceiver and the earth ground, and outputs a signal when the resonant state is present.