Ultrasonic intrusion detection systems employing turbulence discrimination

• US 3,866,198 A
• Filed: 10/17/1973
• Issued: 02/11/1975
• Est. Priority Date: 10/17/1973
• Status: Expired due to Term

• Current Assignee: Leopold Cohen
• Original Assignee: Leopold Cohen
• Inventors: Cohen, Leopold
• Primary Examiner(s): Trafton, David L.
• Application Number:
  US05/407,062
• Time in Patent Office: 482 Days
• Field of Search: 340/258A,258B
• US Class Current: 340/522
• CPC Class Codes: G08B 13/1618 using ultrasonic detection means
• CPC Class Codes: Y10S 367/901 Noise or unwanted signal reduction in nonseismic receiving system

Abstract

There is disclosed an ultrasonic intrusion detection system which is selectively activated and deactivated according to the existence of air turbulence effects as provided by a heating and/or cooling system. The ultrasonic system is deactivated when a heating system is operated and activated when a predesired temperature is achieved resulting in the heating system being inoperative. The operation of the system therefore prevents the ultrasonic intrusion system from operating during air turbulence.

Claims

1. In an intrusion detection system for monitoring a predetermined area, said system, when activated is of the type employing a selected frequency transmitter and a receiver responsive to said transmitted frequency as determined by a Doppler shift due to the presence of an intruder in said area, the combination therewith including apparatus for operating said system in said area in the presence of a generating source of air current turbulence, which source is selectively operated according to environmental conditions of said area, and which air turbulence can undesireably cause said intrusion system to falsely indicate the presence of said intruder, comprising:

a. first means including a thermostat responsive to the operation of said selectively operated generating source to provide a control signal indicative of said operation and therefore of said air turbulence, b. second means coupled to said intrusion system and responsive to said control signal for deactivating said system during the presence of said control signal, whereby said intrusion system is monitoring said area only when said selectively operated source is not operating as determined by said environmental condition.

2. The apparatus accordng to claim 1 wherein said intrusion detection system is of the ultrasonic type.

3. The apparatus according to claim 1 wherein said generating source of air current is a forced air heating or cooling means.

4. An ultrasonic intrusion detection system of the type employing an ultrasonic transmitter for propagating an ultrasonic signal within an area to be protected and a receiver responsive to a change in said transmitted signal evidenced by a Doppler shift caused by the movement of an intruder within said area, in combination therewith apparatus for selectively energizing said system during the absence of propagating air currents which undesirably produce false Doppler shifts, comprising:

a. a thermostat to provide a control signal indicative of the presence of propagating air currents, and b. selectively operated switching means coupled to said ultrasonic system and operative in a first mode to deactivate said system in response to the generation of said control signal and in a second mode to activate said system during the absence of said air currents as monitored by said monitoring means.

5. The apparatus according to claim 4 further comprising:

a. a back-up intrusion system capable of being selectively activated and deactivated and operative when activated to protect said area by means uneffected by said air currents, and b. means coupling said back-up intrusion system to said selectively operated switching means to activate said system only during said first mode, to thereby assure said area is continuously protected.

6. The apparatus according to clAim 4 where said propagating air currents are generated by a forced air heating, air conditioning unit employing a fan causing said propagating air currents to circulate.

7. The apparatus according to claim 6 wherein said monitoring means comprises a thermostat responsive to the temperature within said area as determined by the operation of said forced air heating or air conditioning unit.

8. An intrusion detection system, comprising:

a. an ultrasonic intrusion detection system employing a selectively operated transmitter, receiver apparatus for respectively transmitting an ultrasonic frequency and receiving and detecting a Doppler shift indicative of the presence of an intruder in a predetermined area to be protected, b. a source of circulating air currents operative in a first mode to alter the temperature of said area by circulating forced air currents and in a second stand-by mode determined by the absence of said air currents, said air currents characterized by possessing a velocity indicative of Doppler shifts, c. monitoring means including a thermostat responsive to the operation of said source in said first mode to provide a control signal indicative of such operation, d. control means responsive to said control signal and coupled to said intrusion system to selectively deactivate said intrusion system only during the presence of said control signal whereby said intrusion system is operative only during the absence of said interfering air currents.

9. The system according to claim 8 further comprising:

a. a communications channel coupled to said intrusion system and having an input end responsive to the generator of said Doppler shift to provide a predetermined signal at an output end of said channel for indicting the presence of said intruder, b. means coupling said intrusion detection system to said input end of said channel, said means including means for providing a normal operating signal at said input end when said Doppler shift is not generated, c. a selectively operated back-up intrusion system of the type unaffected by the propagation of said air currents and responsive to said control signal to be selectively operated during said first mode and to be deactivated during the absence of said control signal, and d. means coupling said back-up intrusion system to said input end of said communications channel during said first mode.

10. The apparatus according to claim 9 wherein said back-up system is of the radiation beam generating type for providing a beam of energy about said area, the interruption of said beam being indicative of the presence of an intruder.