发明名称 |
Distance determination and alarm system |
摘要 |
A system has a plurality of transceiver units, including a parent unit and one or more portable and wearable child units, for generating an alarm when a child transceiver unit is more than a predetermined distance away from a parent transceiver unit. The distance is determined by the difference in the phase of a reference signal from the time it is transmitted on an rf signal by a parent unit, received and retransmitted by a child unit, and then received again by the parent unit.
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申请公布号 |
US5661460(A) |
申请公布日期 |
1997.08.26 |
申请号 |
US19950570866 |
申请日期 |
1995.12.12 |
申请人 |
SECURE TECHNOLOGIES, INC. |
发明人 |
SALLEN, ROY;BUDZYNA, WALTER JAMES;SAWABINI, CHARLES E.;SUNSTEIN, DREW E. |
分类号 |
G08B3/10;G01S7/02;G01S13/84;G08B21/00;G08B21/02;(IPC1-7):G08B21/00 |
主分类号 |
G08B3/10 |
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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