Magnetic system for discriminating between vehicles and personnel based upon their characteristic frequency signatures

• US 3,889,181 A
• Filed: 03/08/1974
• Issued: 06/10/1975
• Est. Priority Date: 03/08/1974
• Status: Expired due to Term

• Current Assignee: Charles B. Greer
• Original Assignee: Charles B. Greer
• Inventors: Greer, Charles B.
• Primary Examiner(s): Corcoran, Robert J.
• Application Number:
  US05/449,429
• Time in Patent Office: 459 Days
• Field of Search: 324/41,43R 340/31,38R,38L,258R,258C
• US Class Current: 340/943
• CPC Class Codes: G01R 23/06 by converting frequency into an amplitude of current or voltage
• CPC Class Codes: G01R 27/18 Measuring resistance to earth , i.e. line to ground
• CPC Class Codes: G01V 3/08 operating with magnetic or electric fields produced or modified by objects or geological structures or by detecting devices with electromagnetic waves G01V3/12

Abstract

An electronic system for the detection of moving objects, such as vehicles or personnel, is disclosed. The system detects the presence of vehicles and personnel by utilization of a characteristic frequency signature of each in a twin channel arrangement with each channel adapted to process signals within its respective frequency band. As vehicles may produce signals within the bandpass of both channels and personnel produce signals within the bandpass of only one channel the system is uniquely adapted to distinguish between the two types of moving objects.

Claims

1. A moving object detector and discriminating system which indicates the presence of vehicles and persons and differentiates therebetween comprising:

a first channel means for indicating the presence of a moving vehicle including first bandpass filter input means adapted to pass an input signal having a frequency within a first selected frequency range;

a first level detector electrically connected to said first bandpass filter input means, said first level detector having a selected threshold level and adapted to block signals of lesser amplitude and to pass signals having an amplitude at said threshold level and above;

a moving vehicle presence indicator; and

first channel interconnection means adapted to interconnect the output of said first level detector to said moving vehicle presence indicator to activate same;

a second channel means for indicating the presence of a moving person including second bandpass filter input means adapted to pass an input signal having a frequency within a second selected frequency range;

a second level detector electrically connected to said second bandpass filter input means, said second level detector having a selected threshold level and adapted to block signals of lesser amplitude and to pass signals at said threshold level and above;

a moving person presence indicator and second channel interconnection means adapted to interconnect the output of said second level detector to said moving person presence indicator to activate same;

means for simultaneously applying an input signal, having frequency characteristics representative of the presence of moving objects of the vehicle and person variety, to said first and second channel means; and

channel interrupter means adapted to block passage of the output signal of said second level detector to said moving person presence indicator, said channel interrupter means being responsive to the simultaneous occurence of output signals from said first and second level detectors.

2. A moving object detector and discriminating system as defined in claim 1 wherein:

said first selected frequency range of said first bandpass filter is 6 to 40 hertz, and said second selected frequency range of said second bandpass filter is 0.1 to 2 hertz.

3. A moving object detector and discriminating system as defined in claim 2 wherein:

said first channel interconnector means includes at least one AND gate; and

the output of said first and second level detectors are connected to the inputs of an AND gate in said first channel interconnection means such that said moving vehicle presence indicator is activated in response to the simultaneous occurrence of output signals from said first and second level detectors.