| 摘要 |
PURPOSE:To secure a safety to a surge current, etc., by adding the output of a switch circuit only to a telephone set holding circuit connected to a telephone circuit connected to a calling circuit, and separating completely the telephone circuit connected to the calling circuit and the telephone circuit not connected to the calling circuit. CONSTITUTION:A telephone set provides a first interlocking switch 20 interlocking and changing over to a first change-over switch 18 to change over whether or not the output from a first rectifier circuit 5 connected to a first telephone circuit 1 and connect a first telephone set holding circuit 7 is added to a calling circuit 15 and a second interlocking switch interlocking and changing over to a second change-over switch 19 to change over with the action contrary to the first change-over switch 18 whether or not the output from a second rectifier circuit 6 connected to a second telephone line 2 and connect a second telephone set holding circuit 11 is added to the calling circuit 15. The output of a switching circuit 17 is connected through a first interlocking switch to the first telephone set holding circuit, connected through a second interlocking switch to the second telephone set holding circuit and a first telephone circuit 1 and a second telephone circuit 2 are completely separated.
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