Abstract: A measuring system enabled to simultaneously start measurement by a plurality of transponders by communication between a reader/writer and a plurality of transponders each with a built-in sensor is to be provided. In addition to an identifier SID intrinsic to a sensor and a chip identifier TID intrinsic to a transponder chip, a unique identifier UID combining the sensor SID and the chip TID is provided in each transponder. A reader/writer, in designating a transponder and transmitting a measurement command to it, invalidates the chip TID out of the UID of each transponder, validates only information regarding a sensor function, and transmits measurement commands including action commands unique to each type of sensor.

Abstract: A measuring system enabled to simultaneously start measurement by a plurality of transponders by communication between a reader/writer and a plurality of transponders each with a built-in sensor is to be provided. In addition to an identifier SID intrinsic to a sensor and a chip identifier TID intrinsic to a transponder chip, a unique identifier UID combining the sensor SID and the chip TID is provided in each transponder. A reader/writer, in designating a transponder and transmitting a measurement command to it, invalidates the chip TID out of the UID of each transponder, validates only information regarding a sensor function, and transmits measurement commands including action commands unique to each type of sensor.

Abstract: An RFID which provides a wide working voltage range and general versatility at low cost, without the need for changing its internal circuit design due to external factors. In the RFID, there is provided an arrangement that a low impedance state is given when its internal data communication circuit is in a reset state.

Abstract: For obtaining an IC card low in both power consumption and manufacturing cost, operating conditions in case of going through a contact point, which conditions are associated with supply voltage and signal level in an internal circuit, are to lie within operating conditions in case of going through an antenna. To this end, an IC chip of the IC card is provided with a voltage conversion circuit for lowering a supply voltage supplied through the contact point and a level conversion circuit for lowering the level of a signal fed from the contact point to the internal circuit and raising the level of a signal fed from the internal circuit to the contact point.

Abstract: For obtaining an IC card low in both power consumption and manufacturing cost, operating conditions in case of going through a contact point, which conditions are associated with supply voltage and signal level in an internal circuit, are to lie within operating conditions in case of going through an antenna. To this end, an IC chip of the IC card is provided with a voltage conversion circuit for lowering a supply voltage supplied through the contact point and a level conversion circuit for lowering the level of a signal fed from the contact point to the internal circuit and raising the level of a signal fed from the internal circuit to the contact point.

Abstract: An IC card capable of preventing the occurrence of an abnormal state of coupling and thereby preventing malfunction of IC is provided. The IC card is provided with a coupling detecting means for detecting a contact coupling and a non-contact coupling and is also provided with a communication cut-off means which, when there are supplied electric power and a signal for inducing the other coupling during communication by one coupling, cuts off communication so that communication is performed by neither of the couplings.

Abstract: An object of the present invention is able to provide an IC card in which for example, even if a state should occur in which a plurality of IC cards are piled up in any direction for use, a received signal is not greatly lowered but a normal usage pattern is secured. When the IC cards are piled up with the contours united, a projection drawing of an antenna of one IC card to an antenna surface of the other IC card has an area not overlapped at least 15% or more of an area having an antenna to the other antenna surface on the projection surface and the IC card can work.