ULTRASONIC BURGLAR ALARM SYSTEM

• US 3,721,972 A
• Filed: 02/22/1972
• Issued: 03/20/1973
• Est. Priority Date: 02/22/1972
• Status: Expired due to Term

• Current Assignee: Albert L. Hermans
• Original Assignee: Albert L. Hermans
• Inventors: Hermans, Albert L.
• Primary Examiner(s): Trafton, David L.
• Application Number:
  US05/228,138
• Time in Patent Office: 392 Days
• Field of Search: 340/258R,258B,258D,261,276,275,280
• US Class Current: 340/506
• CPC Class Codes: G08B 13/1609 using active vibration detection systems

Abstract

An ultrasonic burglar alarm system employing one or more transmitters on the exterior of the protected enclosure, and one receiver in the interior of the enclosure. An ultrasonic sound transmission path can exist, but normally it is not completed because of the intervening walls and closed doors and windows of the enclosure. Upon opening of any door or window, or any breaching of the walls, the sound transmission path is completed from exterior to interior, the received sound is detected, and an alarm is given. A supervisory circuit employing exterior receivers is also used, so that if an attempt is made to muffle any exterior transmitter or impair any exterior receiver, an alarm is given.

Claims

1. A burglar alarm system for warning of intrusion into a protected enclosure comprising;

ultrasonic transmitter means, located exteriorly of said protected enclosure, to emit an ultrasonic signal of predetermined frequency;

interior receiver means, located inside said protected enclosure to receive said ultrasonic signal through any opening in said enclosure;

detector means connected to said interior receiver means to detect reception of said ultrasonic signal by said interior receiver means, and to emit an alarm actuating signal if said ultrasonic signal is detected;

alarm means connected to said detector means to sound an alarm upon reception of said alarm actuating signal from said detector means.

2. A burglar alarm system according to claim 1 wherein said ultrasonic transmitter means includes modulating means to modulate the output of said ultrasonic transmitter with a second predetermined frequency, and wherein said detector means includes demodulator means to demodulate said received signal, and to emit an alarm actuating signal only if said demodulated tone of said predetermined frequency is detected.

3. A burglar alarm system according to claim 1 wherein said ultrasonic transmitter means comprises a single ultrasonic transmitter.

4. A burglar alarm system according to claim 1 wherein said protected enclosure comprises a human dwelling place, said ultrasonic transmitter means comprises a plurality of ultrasonic transmitters, each placed exteriorly of every exterior wall surface capable of being breached, and said interior receiver means comprises a plurality of interior receivers, one receiver placed in each room of said dwelling place capable of being entered from the outside.

5. A burglar alarm system according to claim 4, wherein one or more of said interior receivers includes switching means to selectively switch off and on said receivers.

6. A burglar alarm system according to claim 3 wherein said protected enclosure comprises a human dwelling place, and said interior receiver means comprises a plurality of interior receivers, one receiver placed in Each room of said swelling place capable of being entered from the outside.

7. A burglar alarm system according to claim 6, wherein one or more of said interior receivers includes switching means to selectively switch off and on said receivers.

8. A burglar alarm system according to claim 3 wherein said protected enclosure comprises a plurality of jewelry cases in a jewelry store, and said interior receiver means comprises a plurality of interior receivers, one placed in each of said jewelry cases.

9. A burglar alarm system according to claim 8, wherein said interior receivers include switching means to individually switch off and on said receivers.

10. A burglar alarm system for warning of intrusion into a protected enclosure comprising;

ultrasonic transmitter means located exteriorly of said protected enclosure, to emit an ultrasonic signal of predetermined frequency;

monitor receiver means, located exteriorly of said protected enclosure to receive said ultrasonic signal whenever said transmitter is operating;

interior receiver means, located inside said protected enclosure, to receive said ultrasonic signal through any opening in said enclosure;

detector means connected to said interior receiver means to detect reception of said ultrasonic signal by said interior receiver means, and to emit an alarm actuating signal if said ultrasonic signal is detected;

supervisory circuit means connected to said monitor receiver means to detect continuous reception of said ultrasonic signal by said monitor receiver means, and to emit an alarm actuating signal if said continuous reception is interrupted for more than a predetermined period;

alarm means connected to said detector means and to said supervisory circuit means to sound an alarm upon reception of said alarm actuating signal from said detector means or said supervisory circuit means.