发明授权
US5479499A Sensor circuit for voice/fax switch with cascaded amplifier circuit
失效
用于具有级联放大器电路的语音/传真开关的传感器电路
- 专利标题: Sensor circuit for voice/fax switch with cascaded amplifier circuit
- 专利标题(中): 用于具有级联放大器电路的语音/传真开关的传感器电路
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申请号: US167331申请日: 1993-12-15
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公开(公告)号: US5479499A公开(公告)日: 1995-12-26
- 发明人: Katsumi Taniguchi , Hiroyuki Ohta , Shigeru Arai
- 申请人: Katsumi Taniguchi , Hiroyuki Ohta , Shigeru Arai
- 申请人地址: JPX
- 专利权人: Murata Manufacturing Co., Ltd.
- 当前专利权人: Murata Manufacturing Co., Ltd.
- 当前专利权人地址: JPX
- 主分类号: H04M1/82
- IPC分类号: H04M1/82 ; H04N1/327 ; H04M1/00
摘要:
A sensor circuit for telephone line includes a line current detecting circuit (52, 54) which generates a detection signal in response to a line current flowing in a telephone line (20, 22). The detection signal is applied to a first amplifier (56), and the detection signal as amplified is not only further amplified by a second amplifier (57) but also applied to a tone deriving circuit (60) and a CI detecting circuit (61) via a coupling capacitor (59). The detection signal as amplified twice is applied to a comparing circuit (58) which compares the detection signal from the second amplifier with a first reference voltage (V1) and a second reference voltage (V2), so that a line current supervisory signal is outputted from the comparing circuit. The tone deriving circuit includes a band-pass filter and derives a tone signal from the detection signal from the first amplifier. The CI detecting circuit detects a CI (calling tone) on the basis of the detection signal from the first amplifier.
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