发明名称 |
Key system protective apparatus |
摘要 |
A circuit for apparatus to be used with a key system line card for providing electrical isolation between the line circuit and the central office. The adapter responds to ring current from the central office to close a path to the line circuit to cause the line circuit to respond. The circuit provides two-way supervision responding to change of conditions either at the station or at the central office, and also provides a time delay to prevent the circuit from entering the hold condition improperly.
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申请公布号 |
US4194093(A) |
申请公布日期 |
1980.03.18 |
申请号 |
US19780964620 |
申请日期 |
1978.11.29 |
申请人 |
INTERNATIONAL TELEPHONE & TELEGRAPH CORP |
发明人 |
DAVIS, ORLAND L JR;MOORE, CHARLES E JR |
分类号 |
H04M9/00;(IPC1-7):H04M1/00;H04Q5/18 |
主分类号 |
H04M9/00 |
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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