INTRUSION DETECTION SYSTEM AND METHOD USING AN ELECTRET CABLE

• US 3,833,897 A
• Filed: 03/13/1973
• Issued: 09/03/1974
• Est. Priority Date: 03/13/1973
• Status: Expired due to Term

• Current Assignee: James R. Dinger, Marvin D. Laymon, Robert F. Bell, Vytautas V. Pazemenas
• Original Assignee: James R. Dinger, Marvin D. Laymon, Robert F. Bell, Vytautas V. Pazemenas
• Inventors: Laymon, Marvin D., Bell, Robert F., Dinger, James R., Pazemenas, Vytautas V.
• Primary Examiner(s): Swann, III, Glen R.
• Application Number:
  US05/340,849
• Time in Patent Office: 539 Days
• Field of Search: 340/258R,261
• US Class Current: 367/136
• CPC Class Codes: G08B 13/122 for a perimeter fence features peculiar to electrified fences A01K3/00
• CPC Class Codes: G08B 13/169 using cable transducer means

Abstract

An intrusion detection system comprises a fence mounted coaxial electret cable connected to remote signal processing apparatus which includes both automatic alarm circuits and a loudspeaker, the latter producing sounds generated by audio frequency signals propagating on the cable. The automatic alarm circuit responds to cable signals that meet predetermined criteria for bandpass, amplitude and duration to indicate a suspected intrusion; the loudspeaker reproduces sounds caused by the condition which produces the alarm and permits the operator to aurally determine the nature of the condition for verifying in real time its valid or spurious character. The signals on the cable may be manually or automatically switched to the loudspeaker or may be continuously connected to it as required or desired.

Claims

1. A system for detecting and identifying a source of mechanical vibrations in a solid body comprising a coaxial electret cable, means for mechanically externally coupling to said cable the mechanical vibrations produced in said body by said source whereby electrical signals are generated by said cable, said signals having a frequency in the audio range, an alarm device, a signal processor electrically connected to said cable and having a first output connected to said device and a second output comprising said audio frequency signals, said processor being responsive to certain of said electrical signals having predetermined characteristics for producing said first output for automatically energizing said alarm device, and transducer means electrically connectable to said second output and responsive to said audio frequency signals for converting same into sound waves.

2. The system according to claim 1 with automatic switch means connecting to said transducer means said second output of the processor in response to the energizing of said alarm device by the first output from said processor.

3. The method of detecting targets traversing an area protected by a fence consisting of the steps of tightly mechanically coupling a coaxial electret cable to the body of the fence and causing vibrations produced on the fence by a target to be coupled to said cable whereby electrical signals are generated by said cable, automatically actuating an alarm device solely in response to certain of said electrical signals having parameters characteristic of signals generated by the target, and energizing loudspeaker means with all of said electrical signals and aurally verifying the nature of the source of said vibrations to determine whether the alarm is true or false.

4. The method according to claim 3 in which said loudspeaker means is energized after actuation of the alarm device.

5. The method according to claim 3 in which energization of said loudspeaker means is independent of the actuation of the alarm device.

6. The method according to claim 5 in which said energization of the loudspeaker means is automatic after actuation of the alarm device and is responsive to all electrical signals generated by said cable.

7. The method of detecting intrusions of an area protected by a coaxial electret cable tightly coupled to a solId body consisting of converting into sound waves electrical signals generated on said cable by vibrations transferred to the cable from the body whereby an operator is enabled to aurally determine the nature of the condition producing said vibrations.

8. In combination, a solid body capable of transmitting mechanical vibrations produced by a condition to be monitored, a coaxial electret cable, means for mechanically coupling said cable to said body whereby said vibrations cause said cable to generate an electrical signal, and means responsive to said electrical signal for indicating the character of the condition being monitored and comprising transducer means for converting signals having audio frequencies into sound waves.