| 摘要 |
PROBLEM TO BE SOLVED: To provide a low-frequency detector for a telephone which can highly sensitively detect a low-frequency signal such as a calling signal to be transmitted to a subscriber branch line, and is used as a specific technical means more suitable for practical use. SOLUTION: Upon sensing a change in leakage electric field generated from the subscriber branch line 50, a sensor circuit 6 outputs a predetermined detection signal corresponding to that. The circuit 6 is mainly provided with an antenna plate 7 and a capacitor 8 for sensor. The antenna plate 7 receives the leakage electric field changing in the vicinity of the subscriber branch line 50 when a calling signal is transmitted to the subscriber branch line 50, using electrostatic induction at a position approximate to the subscriber branch line 50. The antenna plate 7 is made of a conductive material and formed into a substantially rectangle plate, and its upper surface abuts and is bonded on the inner wall surface of a case body 2. Further, the external surface of an upper side of the capacitor 8 for sensor is bonded on the lower surface of the antenna plate 7. COPYRIGHT: (C)2008,JPO&INPIT
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