发明名称 |
Frequency selective ringer circuit |
摘要 |
A frequency selective ringer circuit which utilizes a constant current source in conjunction with an array of resistors and switches for developing a frequency selective window with which to detect an incoming frequency at the tip and ring inputs of a telephone system. The incoming frequency is doubled and converted to a d.c. level which is utilized as the converted level which is evaluated by the circuit. Where the converted voltage level falls within the established window, a drive circuit is energized for actuating a transducer such as a piezoelectric crystal or loudspeaker. Frequency selection is made by the simple expedient of closing one of a plurality of SPST switches. The circuit also may include a circuit for automatically deactivating the mechanical bell of an existing telephone set without the removal thereof.
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申请公布号 |
US4653093(A) |
申请公布日期 |
1987.03.24 |
申请号 |
US19850759462 |
申请日期 |
1985.07.26 |
申请人 |
FLOYD BELL ASSOCIATES, INC. |
发明人 |
ZOFAN, ELY S. |
分类号 |
H04Q5/10;(IPC1-7):H04M1/00 |
主分类号 |
H04Q5/10 |
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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