| 摘要 |
PURPOSE:To decrease noise existing much on a cable by providing a switch to a path of a reverse signal transmitted from a subscriber to a central station being a signal transmission line of an external control unit and controlling the switch to be turned on as required. CONSTITUTION:A program routine is started from the step 140 and the step 141 makes decision whether or not a data is designated from the central station 11. When the designation of the central station 11 is decided, a forward data is decoded in the step 141. Then the step 142 makes decision which of instructions turning on or off a switch 47B is incoming. When the instruction turning off the switch 47B exists, the step moves to the step 43, the switch 47B is turned off, the step moves to the step 140, and when the instruction turning on the switch 47B exists, the step moves to the step 144, the switch 47B is turned on and the step moves to the step 140.
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