| 摘要 |
PURPOSE:To decrease the number of connection signal lines between a telephone set and a main body by using a transmission signal line so as to send a hook signal. CONSTITUTION:Since a telephone set 20 is parted from a base at off-hook, a magnetic sensor integrated circuit 3 does not sense the magnetism of a magnet in the base and opens an output terminal 8. Thus, a current flows to a base 9 of a transistor (TR) 4 to make the collector 10 and the emitter 11 conductive. As a result, an AC signal superimposed with a DC signal (hook signal) is sent to a main body 25 via a telephone signal line 21, and the main body 25 uses the capacitor 13 to separate the AC signal and the DC signal. That is, the AC signal is outputted to a terminal 14 through the capacitor 13 and the DC signal is cut off by the capacitor 13 and given to the resistor 12.
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