ALARM DETECTOR WITH INCREASED OPERATING RANGE

• US 3,786,467 A
• Filed: 03/22/1972
• Issued: 01/15/1974
• Est. Priority Date: 03/22/1972
• Status: Expired due to Term

• Current Assignee: Elektrowatt AG Bellerivestrasse
• Original Assignee: William L. Cotter
• Inventors: Cotter, William L.
• Primary Examiner(s): Trafton, David L.
• Application Number:
  US05/236,868
• Time in Patent Office: 664 Days
• Field of Search: 340/258A,258B,15,16R
• US Class Current: 340/533
• CPC Class Codes: G08B 13/1627 using Doppler shift detection circuits

Abstract

In an ultrasonic alarm detector of the doppler detection type including a transmitter transducer and a receiver transducer, the improvement comprising a second transmitter transducer disposed remote from the detector and driven from the master oscillator at the detector. The second transmitter is preferably disposed at the limiting range of the alarm detector and is directed in the same direction as the transmitter transducer at the alarm detector thereby extending the operating range of the detector to up to twice the range attainable without the second transmitter transducer.

Claims

1. In an alarm detection system for use in a secured area comprising a detector having means for generating an ultrasonic signal, first means for transmitting the ultrasonic signal to establish an ultrasonic wave pattern in the area, means for receiving the reflected ultrasonic signal, said first means for transmitting and said means for receiving being disposed at a first site, and means for registering a doppler signal of a frequency corresponding to the velocity of motion in the area including means for registering an alarm condition, the improvement comprising;

second means for transmitting an ultrasonic signal coupled from and responsive to said means for generating an ultrasonic signal, said second means for transmitting being disposed at a second site remote from the first transmitting means and directed so as to extend the detection range of said system, said means for registering a doppler signal capable of being responsive to said second means for transmitting, said first means for transmitting including a transmitter transducer, said means for receiving including a receiver transducer, and said second means for transmitting including a transmitter transducer, and means for coupling the ultrasonic signal to said second means for transmitting and including a multi-wire tie line.

2. The system of claim 1 wherein said second means for transmitting is disposed within the detection range of said detector when operated independently without said second means for transmitting connected.

3. The system of claim 2 wherein said second means for transmitting is disposed at about the maximum range of said detector to thereby extend the composite range to twice the original range.

4. The system of claim 1 wherein said buffer circuit includes a resonant circuit and amplifier means both coupled to said second transmitter transducer.

5. The system of claim 4 wherein said resonant circuit includes a tank circuit and said amplifier means includes a transistor coupled to said tank circuit.

6. The system of claim 5 wherein said tie line includes a power line, return line and signal line.

7. An Alarm detection system for use in an area to be secured comprising;

an oscillator for providing an ultrasonic signal, first transmitting means including a first transmitter transducer for directing the ultrasonic signal into the secured area to establish an ultrasonic wave pattern in a first part of the secured area, means for receiving the reflected ultrasonic signal, said first transmitting means and said means for receiving being disposed at a first site, means responsive to said first transmitting means and said means for receiving for registering a doppler signal of a frequency corresponding to the velocity of motion in the area including means for registering an alarm condition, second transmitting means including a secoNd transmitter transducer disposed at a second site remote from said first site and directed toward and having an operating range covering a second part of the secured area, and means coupling said ultrasonic signal to said second transmitter transducer.

8. In an alarm detection system for use in a secured area, said system comprising first means for transmitting an ultrasonic signal to establish an ultrasonic wave pattern in the area, means for receiving the reflected ultrasonic signal, and means for registering a doppler signal of a frequency corresponding to the velocity of motion in the area the improvement comprising;

second means for transmitting an ultrasonic signal, said first means for transmitting being disposed at a first site and having an operating range covering a first portion of the secured area, said means for receiving being disposed at the first site, said second means for transmitting being disposed at a second site remote from said first means for transmitting and directed toward and having an operating range covering a second portion of the secured area, said means for registering being responsive to reflected signals from both said first and second means for transmitting.

9. The system of claim 8 wherein said second means for transmitting is disposed approximately at the limiting range of said first means for transmitting.

10. The system of claim 8 comprising conductive means for coupling the ultrasonic signal to said second transmitting means.

11. The system of claim 8 wherein said first means for transmitting is directed in a first direction and said second means for transmitting is directed in a second direction approximately orthogonal to said first direction.