| 摘要 |
PURPOSE:To efficiently execute a data transmission by setting automatically such a receiving condition as a receiving condition of a sensor side becomes optimum between a sensor and a hand held terminal, by using a constant-current pulse being suitable for a long distance transmission. CONSTITUTION:In case of executing the communication between a hand held terminal HHT2 and a sensor SNR', prior to the communication, a check as to whether a transmission system is under the condition conforming to the communication or not is executed from the hand held terminal HHT2 side by using a series/parallel converter SCI2', a parallel/series converter SCI1', an impedance control circuit IMP, and a microprocessor muP2. The impedance control circuit IMP holds a voltage Er in a holding circuit Q1 by opening and closing a switch SW1 by a control signal S1 from the microprocessor muP2, changes a level of an output of an inverter G1 by controlling a transistor Q2, supplies an impedance control signal S2 into the series/parallel converter SCI2' and lowers its receiving impedance. In such a way, a data transmission can be executed efficiently.
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