DATA TRANSMITTER

PURPOSE:To make the transmitter small and to reduce the power by sending a data signal depending on a content of data to be sent when a trailing ridge of a reception signal is detected so as to eliminate the need for an oscillation circuit to activate a clock means. CONSTITUTION:A transmission reception coil of a data carrier receives a power carrier signal SL1 sent from a transmission coil of an antenna, and the transmission reception coil is resonated by driving transistors(TRs) to send a data signal SL2a. In this case, the data signal SL2a is sent from the data carrier in a timing synchronously with a transmission end timing of the power carrier signal SL1 sent from the antenna. Thus, even when a charge end timing of a capacitor C1 is delayed due to a change in the distance between the antenna and the data carrier, the data signal is sent from the data carrier at an intermittent point of the power carrier signal SL1 at all times and then the transmission reception of data are accurately conducted.