Patent · US Expired

Burglar alarm device

US4275390A · kind A · utility

24Cited by

6References

12Claims

0Family size

Assignee

Siemens Aktiengesellschaft · DE

Inventors

Walter Heywang · Grasbrunn, DE
Max Guntersdorfer
Peter Kleinschmidt · Munich, DE

Key dates

Filing date	Mar 24, 1977
Grant date	Jun 23, 1981
Priority date	—
Expiry date	Mar 24, 1997

Classification

Technology area (CPC G)Physics
CPC primaryG08B13/2494
WIPO fieldControl
WIPO sectorInstruments

Abstract

Burglar alarm apparatus includes an ultrasonic transmitter and an electromagnetic radiation transmitter whose signals are Doppler frequency shifted by an object moving through the radiation fields, the signals being received by respective demodulating receivers which provide respective electrical signals corresponding to the Doppler frequency. Frequency conversion apparatus is connected to one of the receivers to convert the output frequency thereof by a predetermined ratio to normalize or equalize the frequencies and a signal comparison circuit is provided to produce a signal in response to a ratio of the Doppler shifted signals within a predetermined tolerance range.

Source: USPTO / EPO open patent data. Objective bibliographic and citation counts.