PURPOSE: To obtain a card which is small in size, light in weight and has multiple functions by providing the functions of a reception and a transmission to a passive mixer.

CONSTITUTION: When two different frequencies are added to a mixer being a nonlinear element, the frequencies are enabled to be converted into the frequency of the sum and the difference of each frequency. When the radio waves of each different frequency are added to a card from an external transmitter, each frequency is received as it is by the detector on the card and the frequencies are added to the mixer by using this characteristic, the signal of the sum and difference of the frequency added from the outside can be obtained. When a modulation is performed for this signal by the data of the memory incorporated into the card and the signal is transmitted from the card, the transmission of the signal is enabled by the frequency which has conversion loss but is different from a transmission frequency. When the transmission frequency is properly selected and the frequency which is difficult to receive the disturbance of the transmission frequency is selected by the frequency of the sum or difference of the transmission frequency, the data of the card becomes possible to be received while keeping the transmitter operating.