Abstract: A sensor includes a substrate, a medium on which a surface acoustic wave propagates, a reference electrode, an antenna, a transducer that includes a first electrode connected to the antenna and a second electrode connected to the reference electrode and arranged opposite to the first electrode, and that has a function of converting a signal received by the antenna into a surface acoustic wave propagating on the medium, and a function of converting a surface acoustic wave propagating on the medium and reaching the transducer into a signal and outputting the signal to the antenna, a reflector that throws back a surface acoustic wave generated by the transducer, propagating on the medium, and reaching the reflector, toward the transducer, and an impedance converter connected to the reference electrode, impedance of which changes in response to a change in circumstances surrounding the sensor.

Abstract: A responder authenticity determination system, comprising: a responder that sends a response signal in response to a received signal; an interrogation signal generator that generates an interrogation signal having a random waveform; a transceiver that sends the generated interrogation signal to the responder, and receives a response signal from the responder; and an authenticity determination unit that determines authenticity of the responder based on the received response signal and the random waveform of the generated interrogation signal.

Abstract: A sensor of this comprises a receiving section that receives a signal that is sent from outside, a circuit whose impedance changes irreversibly in accordance with an environmental change, a measurement section that measures the impedance of the circuit in an event that a signal is received by the receiving section, and a sending section that sends data representing a measurement result of the measurement section.

Abstract: A wireless terminal holder includes a body that attachably accommodates a wireless terminal that exchanges radio waves via an antenna, an antenna unit attached to the body and that is of sufficient strength to freely support the body, and that functions as the antenna for the wireless terminal when connected to an antenna terminal of the wireless terminal, and a connector attached to the body that connects the antenna unit to the antenna terminal of the wireless terminal, with the wireless terminal being accommodated in the body.

Abstract: An activity history record apparatus includes a portable receiver that receives information, which contains position information and which is transmitted from a transmitter disposed at a predetermined position. The receiver includes a reception section, a voice detection section and a storage section. The reception section receives the information. The voice detection section detects voice. The storage section stores the position information extracted from the received information and voice-related information derived from the voice detected by the voice detection section, as a history.

Abstract: A sensor includes: a receiver that receives signals sent from outside; a first converter that converts signals received by the receiver into acoustic waves; a second converter that converts the acoustic waves propagating along a predetermined area into signals; a transmitter that transmits the signals that are output from the second converter; and an attachment that is attached to a propagation path of the acoustic waves on the predetermined area, that undergoes an irreversible change in response to an environmental change and that changes the propagation characteristics of the acoustic waves on the predetermined area due to this change.

Abstract: An utterance state detection apparatus includes a transmission device carried by a user and one or more reception devices. The transmission device includes an identification-information storage unit, a speech detector and a transmission unit. The identification-information storage unit stores identification information of at least one of the transmission device and the user. The speech detector detects speech. The transmission unit transmits transmission information including information of the detected speech and the identification information. The reception devices are installed in regions. Each reception device includes an utterance-state detector.