发明名称 |
Sensor circuit for voice/fax switch with cascaded amplifier circuit |
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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申请公布号 |
US5479499(A) |
申请公布日期 |
1995.12.26 |
申请号 |
US19930167331 |
申请日期 |
1993.12.15 |
申请人 |
MURATA MANUFACTURING CO., LTD. |
发明人 |
TANIGUCHI, KATSUMI;OHTA, HIROYUKI;ARAI, SHIGERU |
分类号 |
H04M1/82;H04N1/327;(IPC1-7):H04M1/00 |
主分类号 |
H04M1/82 |
代理机构 |
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代理人 |
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主权项 |
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地址 |
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