The patent badge is an abbreviated version of the USPTO patent document. The patent badge does contain a link to the full patent document.
The patent badge is an abbreviated version of the USPTO patent document. The patent badge covers the following: Patent number, Date patent was issued, Date patent was filed, Title of the patent, Applicant, Inventor, Assignee, Attorney firm, Primary examiner, Assistant examiner, CPCs, and Abstract. The patent badge does contain a link to the full patent document (in Adobe Acrobat format, aka pdf). To download or print any patent click here.
Patent No.:
Date of Patent:
Jun. 23, 1981
Filed:
Mar. 24, 1977
Applicant:
Inventors:
Assignee:
Siemens Aktiengesellschaft, Berlin & Munich, DE;
Primary Examiner:
Assistant Examiner:
Int. Cl.
CPC ...
G08B / ; G08B / ; G08B / ;
U.S. Cl.
CPC ...
340554 ; 343 / ; 343 / ; 343-77 ; 367 94 ;
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.