| 摘要 |
PURPOSE:To attain stable data transmission by allowing a slave station to change the impedance of the own station to a transmission line according to the data to be sent and allowing a master station to detect the change in the impedance of the slave station so as to receive the data of the slave station. CONSTITUTION:The slave station 18 to transmit a data to the master station uses a modulator 24 inserted between a signal line 19 connected to the electric line and a grounding point 20 so as to change the impedance between the electric line 8 and the ground point 20 according to the data. The impedance in this case may be the impedance change depending on resistance/capacitance/ inductance and they are changed independently or together. The impedance change with respect to the electric line in the slave station is caused as a level change of the effective component of a measuring low frequency signal circulating to the ground line in the master station and in detecting the impedance change, the data from the slave station is received by the master station.
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