发明授权
- 专利标题: Distance determination and alarm system
- 专利标题(中): 距离确定和报警系统
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申请号: US570866申请日: 1995-12-12
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公开(公告)号: US5661460A公开(公告)日: 1997-08-26
- 发明人: Roy Sallen , Walter James Budzyna , Charles E. Sawabini , Drew E. Sunstein
- 申请人: Roy Sallen , Walter James Budzyna , Charles E. Sawabini , Drew E. Sunstein
- 申请人地址: MA Boston
- 专利权人: Secure Technologies, Inc.
- 当前专利权人: Secure Technologies, Inc.
- 当前专利权人地址: MA Boston
- 主分类号: G08B3/10
- IPC分类号: G08B3/10 ; G01S7/02 ; G01S13/84 ; G08B21/00 ; G08B21/02
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.
公开/授权文献
- US5056645A Coin operated telephone payment device 公开/授权日:1991-10-15