Remotely responsive motion detector
US4144529A · kind A · utility
Assignee
Inventors
Key dates
| Filing date | May 20, 1977 |
| Grant date | Mar 13, 1979 |
| Priority date | — |
| Expiry date | May 20, 1997 |
Classification
- Technology area (CPC G)Physics
- CPC primaryG08B13/26
- WIPO fieldControl
- WIPO sectorInstruments
Abstract
A motion detector comprising a self-excited oscillator operating in the megacycle range which is maintained at a substantially fixed frequency by way of a constant current source. By virtue of the constant current input changes in inductance and capacitance associated with the motion of the intruder are registered as changes in oscillatory amplitude rather than frequency change. This change in amplitude is passed through a low band pass filter, i.e. a filter operating in the range of frequencies normally associated with the motion of a human, and the changes in this filtered signal are then passed through a coupling capacitor to a comparator. In this manner, the DC level, which often drifts in a linear circuit is taken out. The output of the comparator is then applied to a coded transmitter which on the occurrence of an intrusion will set off an alarm at a remotely held receiver.
Source: USPTO / EPO open patent data. Objective bibliographic and citation counts.