发明名称 |
APPARATUS AND METHOD FOR DETECTING TELEPHONE LINE STATUS |
摘要 |
Telephone line status indication is improved by making measurements of the differential voltage across the Tip-Ring terminals of a telephone set (100). The telephone set is connected to a telephone line which is shared with other parallel-connected telephone sets. The measurement of differential line voltage is made each time the set changes state (i.e., between on-hook and off-hook). The maximum magnitude of one of the last three measurements is stored to represent the on-hook state, and is arithmetically averaged with the maximum magnitude of one of the last three stored for the off-hook state to create a reference voltage. The reference voltage is updated each time the telephone set changes state and is continually compared with the present differential line voltage to determine which one is larger. A light-emitting-diode (110) on the telephone set indicates that the telephone line is in use whenever the reference voltage exceeds the measured differential line voltage.
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申请公布号 |
CA2118731(C) |
申请公布日期 |
1997.11.18 |
申请号 |
CA19942118731 |
申请日期 |
1994.03.10 |
申请人 |
AMERICAN TELEPHONE AND TELEGRAPH COMPANY |
发明人 |
STAHL, THOMAS ANTHONY;KARPICKE, JOHN ARTHUR;MEANS, DONALD RICHARD;BURGER, THEODORE OTHMAR;KEEN, DONALD MARION;WITTMAN, BRIAN ALBERT |
分类号 |
H04M1/82;(IPC1-7):H04M1/24;H04M1/72 |
主分类号 |
H04M1/82 |
代理机构 |
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