| 摘要 |
PURPOSE:To eliminate the need for a special circuit for detecting the length of line and a setting switch for line length information or the like by including the line length information till a terminal equipment automatically to its transmission signal at the reply of the terminal equipment. CONSTITUTION:A master station 10 sends a synchronizing signal being the periodic voltage division of a DC power voltage VD to a transmission line 20 via resistors R1, R2. A terminal equipment 100 sends the transmission data through the combination of the operation closing/opening the transmission line 20 via resistor R3 synchronously with the said synchronizing signal, the master station 10 measures the potential of the transmission line via an A/D converter at that time and detects the length of line till the replied terminal equipment 100. Thus, the master station detects the line length information till the replied terminal equipment automatically at the reply of the terminal equipment to the master station.
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