Distance determination and alarm system
US5661460A · kind A · utility
132Cited by
16References
36Claims
0Family size
Assignee
Inventors
Key dates
| Filing date | Dec 12, 1995 |
| Grant date | Aug 26, 1997 |
| Priority date | — |
| Expiry date | Dec 12, 2015 |
Classification
- Technology area (CPC G)Physics
- CPC primaryG08B21/023
- WIPO fieldControl
- WIPO sectorInstruments
Abstract
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.
Source: USPTO / EPO open patent data. Objective bibliographic and citation counts.