Patent ID: 6952167

Claim:
A noncontact communications medium comprising: a resonant circuit including: an antenna coil which generates an induced electromotive force by receiving electromagnetic waves carrying information as a result of changes in the amount of electric power and thereby transmits and receives signals; two capacitors parallel-connected to the antenna coil; a main circuit which processes a received signal obtained by demodulating an output of said resonant circuit and outputs a modulated transmitting signal to said resonant circuit; a switch section which switches first one of said two capacitors between a connected state and a disconnected state; and a switch control section which controls switching operation of said switch section according to the amount of an output voltage occurring in said resonant circuit and according to a specific change in said output voltage, wherein said switch control section controls the switching operation of said switch section according to a change in a rising edge of said output voltage when the output voltage occurring in said resonant circuit is equal to or higher than a specific value.