Siren detector
US4864297A · kind A · utility
Assignee
Inventors
Key dates
| Filing date | Oct 14, 1987 |
| Grant date | Sep 5, 1989 |
| Priority date | — |
| Expiry date | Oct 14, 2007 |
Classification
- Technology area (CPC G)Physics
- CPC primaryG08G1/087
- WIPO fieldControl
- WIPO sectorInstruments
Abstract
A siren detector for detecting siren sounds which precess at known yelp, wail and high-low warble rates within a selected frequency band. A transducer detects siren sounds and produces a corresponding electrical output signal. The output signal is filtered to reject signal frequencies outside the selected frequency band. The signal amplitude is monitored and varied as required to produce a constant amplitude output signal. The constant amplitude output signal is low pass filtered for detection of siren high-low sounds and is also low pass filtered for detection and output of precession signals which pass through a selected center frequency. Subsequent filters are provided for detecting signals which vary at the wail and yelp warble rates. Wail, high-low and yelp warble rate signals output by the various filters respectively trigger wail and yelp clock generators which in turn drive don't walk and red light output flip-flops respectively. Operation of the red light output flip-flop is controlled by a delay mechanism which provides a further filtration level to prevent false triggering.
Source: USPTO / EPO open patent data. Objective bibliographic and citation counts.