Patent US3717864A successfully refreshed from Google Patents.
US3717864A
Expired / Lapsed
US
⏱️ 0.0 years remaining
Periodic event detector system
Assignee: TDY Industries LLC
•
Filing: 1971-11-02
•
Granted: 1973-02-20
•
Expires: 1991-11-02
Abstract
Abstract An intrusion detector system for detecting periodic events such as footsteps in the illustrative example, such events being picked up by a vibration transducer and being distinguished from other random vibration events by virtue of their regular periodicity, the system using ordinary frequency and amplitude techniques in early stages to eliminate undesirable vibrational waves or ''''signatures'''' which are probably not attributable to footstep events, and then using digital filtering techniques to detect significant periodicity among the filtered event signals remaining. The system uses the latter techniques to clock such event signals comprising discrete energy bursts through long shift registers at clock rates which are high as compared with the rate of occurrence of the events, and then employs many different groups of sampling gates to examine differently spaced stages in the shift registers to test for different periodicities. The system further compares periodicity determinations made in this way using digital techniques with characteristics of the incoming event signals themselves to ascertain whether at any particular time the number of event signals which actually result in detections of periodicities is reliably high.
Inventors
- 👤 J Cook
- 👤 M Wilt
Bibliographic Details
Application Number
—
Jurisdiction
US
Data Source
google_patents
Last Synchronized
2026-10-24 21:57
CPC Classifications
G; G08; G08B; G08B13/00; G08B13/16; G08B13/1654; G08B13/1663
Claims Analysis
Total Claims: 14
Claim 1
Independent Claim
195 words
A system for detecting and indicating vibrational events of interest recurring at a periodic rate in the presence of other events occurring at random, comprising: a. means for picking up vibrations representing said events and converting them into electrical event signals; b. a source of clock pulses occurring at a rate in excess of the rate of occurrence of events of interest to which the system is intended to respond; c. multiple stage shift register means connected to receive said event signals, said source being connected to said register means to shift said event signals through its stages at the rate of said clock pulses; d. plural periodicity detecting channels each having an output and each having a group of AND gate means with multiple inputs respectively connected to periodically spaced stages of the shift register means, and each channel being operative to deliver an output signal when the stages to which the inputs of its AND gates are connected are simultaneously responding to correspondingly-spaced event signals; and e. means connected to the outputs of said channels and operative in response to an output signal appearing therein to indicate the detection of periodically related events.
Claim 2
Independent Claim
195 words
A system for detecting and indicating vibrational events of interest recurring at a periodic rate in the presence of other events occurring at random, comprising: a. means for picking up vibrations representing said events and converting them into electrical event signals; b. a source of clock pulses occurring at a rate in excess of the rate of occurrence of events of interest to which the system is intended to respond; c. multiple stage shift register means connected to receive said event signals, said source being connected to said register means to shift said event signals through its stages at the rate of said clock pulses; d. plural periodicity detecting channels each having an output and each having a group of AND gate means with multiple inputs respectively connected to periodically spaced stages of the shift register means, and each channel being operative to deliver an output signal when the stages to which the inputs of its AND gates are connected are simultaneously responding to correspondingly-spaced event signals; and e. means connected to the outputs of said channels and operative in response to an output signal appearing therein to indicate the detection of periodically related events.
Claim 3
Independent Claim
195 words
A system for detecting and indicating vibrational events of interest recurring at a periodic rate in the presence of other events occurring at random, comprising: a. means for picking up vibrations representing said events and converting them into electrical event signals; b. a source of clock pulses occurring at a rate in excess of the rate of occurrence of events of interest to which the system is intended to respond; c. multiple stage shift register means connected to receive said event signals, said source being connected to said register means to shift said event signals through its stages at the rate of said clock pulses; d. plural periodicity detecting channels each having an output and each having a group of AND gate means with multiple inputs respectively connected to periodically spaced stages of the shift register means, and each channel being operative to deliver an output signal when the stages to which the inputs of its AND gates are connected are simultaneously responding to correspondingly-spaced event signals; and e. means connected to the outputs of said channels and operative in response to an output signal appearing therein to indicate the detection of periodically related events.
Claim 4
Independent Claim
195 words
A system for detecting and indicating vibrational events of interest recurring at a periodic rate in the presence of other events occurring at random, comprising: a. means for picking up vibrations representing said events and converting them into electrical event signals; b. a source of clock pulses occurring at a rate in excess of the rate of occurrence of events of interest to which the system is intended to respond; c. multiple stage shift register means connected to receive said event signals, said source being connected to said register means to shift said event signals through its stages at the rate of said clock pulses; d. plural periodicity detecting channels each having an output and each having a group of AND gate means with multiple inputs respectively connected to periodically spaced stages of the shift register means, and each channel being operative to deliver an output signal when the stages to which the inputs of its AND gates are connected are simultaneously responding to correspondingly-spaced event signals; and e. means connected to the outputs of said channels and operative in response to an output signal appearing therein to indicate the detection of periodically related events.
Claim 5
Dependent Claim
126 words
In a system as set forth in claim 1, said shift register means comprising separate multiple-stage shift registers; the source of clock pulses including means for delivering clock pulses at different rates to each of said shift registers; and the channels whose AND gate inputs are connected to stages having the smallest spacings for the purpose of detecting events having the highest recurrence rates being coupled to the shift register which is driven by the source at the highest clock pulse rate, and the channels whose AND gate inputs are connected to stages having the greatest spacings for the purpose of detecting events having the lowest recurrence rates being coupled to the shift register which is driven by the source at the lowest clock pulse rate.
Claim 6
Dependent Claim
111 words
In a system as set forth in claim 1, the inputs of the AND gates in the groups which comprise the different channels being respectively connected to said stages with different spacings along the shift register means to detect event signals having different periodicities as they are shifted through the register means; and the various channels including channels whose AND gate inputs are all mutually spaced by exactly the same number of stages, and further including other channels whose AND gate inputs are mutually spaced by staggered numbers of stages, the latter channels being operative to detect periodic event signals whose periodicities are not closely related to the clock pulse rate.
Claim 7
Dependent Claim
126 words
In a system as set forth in claim 3, said shift register means comprising separate multiple-stage shift registers; the source of clock pulses including means for delivering clock pulses at different rates to each of said shift registers; and the channels whose AND gate inputs are connected to stages having the smallest spacings for the purpose of detecting events havinG the highest recurrence rates being coupled to the shift register which is driven by the source at the highest clock pulse rate, and the channels whose AND gate inputs are connected to stages having the greatest spacings for the purpose of detecting events having the lowest recurrence rates being coupled to the shift register which is driven by the source at the lowest clock pulse rate.
Claim 8
Dependent Claim
62 words
In a system as set forth in claim 3, the AND gate inputs in each channel including at least three inputs all connected to spaced ones of said stages and all of the inputs in any channel having to simultaneously detect an event signal in the stage to which it is connected before the channel can have a signal at its output.
Claim 9
Dependent Claim
147 words
In a system as set forth in claim 1, rate detector means for comparing the rate of arrival of electrical event signals with the rate of detection of periodically related event signals as indicated by output signals from said channels, said rate detector means being interposed between the outputs from the channels and the said means for indicating periodically related events, and the rate detector means having means operative to pass output signals to the indicating means when the rate of arrival of event signals is within a predetermined ratio with respect to the rate of said output signals whereby most of the event signals are periodically mutually related, and further having means operative to block said output signals to the indicating means when the rate of arrival of the event signals is outside of said ratio whereby many of the event signals are of random nature.
Claim 10
Dependent Claim
109 words
In a system as set forth in claim 1, means for wiping out from the stages of the register means electrical event signals occurring at a rate which is higher than the rate to which the system is intended to respond and which approaches or exceeds said clock pulse rate, comprising AND gates having inputs connected to the first few stages of the register means and operative to be enabled when several of said stages in close mutual proximity are simultaneously responding to event signals, and said gates having outputs each connected and operative when its gate is enabled to reset said first few stages of the register means.
Claim 11
Dependent Claim
85 words
In a system as set forth in claim 1, said means for picking up events and converting them into electrical signals comprising, a geophone; AGC amplifier means connected to said geophone to amplify its output; bandpass filter means connected to said amplifier means and having an AC passband restricted to pass only frequencies which are dominant in signatures of predetermined vibrational events of interest; and level detector means having an adjustable threshold level and operative to pass only electrical signals whose amplitudes exceeds said level.
Claim 12
Dependent Claim
66 words
In a system as set forth in claim 1, said events of interest comprising human footsteps having waveform signatures which when detected comprise a damped series of impulses, and said means for converting the events to electrical signals including minimum pulse width detector means operative to pass impulses whose widths exceed a preset minimum duration and to block impulses whose width is less than said minimum.
Claim 13
Dependent Claim
129 words
In a system as set forth in claim 9, said footstep events of interest occurring at rates approximately within the range of one to two-and-one-half events per second, and said shift register means comprising two shift registers, said source of clock pulses including means for delivering clock pulses at the rate of about 10.5 Hertz to one shift register and for delivering clock pulses at the rate of about 5.25 Hertz to the other shift register, and those of the channels which are operative to detect events having the highest recurrence rates having their AND gate inputs connected to said one shift register and the other channels which are operative to detect events having the lowest recurrence rates having their AND gate inputs connected to said other shift register.
Claim 14
Dependent Claim
169 words
In a system as set forth in claim 1, rate detector means for comparing the rate of arrival of electrical event signals with the rate of detection of periodically related event signals as indicated by output signals from said channels, said rate detector means being interposed between the outputs from the channels and the said means for indicating periodically related events, said rate detector means comprising a first counter connected to receive said channel output signals and operative to count a first number of them before delivering its own first output; a second counter connected to receive said electrical event signals and operative to count a second number of them, larger than said first number, before delivering its own second output; a flipflop connected to be set by each channel output signal and to be reset by each second output from the second counter, and the flipflop having an output in reset condition operative to clear both counters; and means connecting said first output to actuate said indicating means.
References Cited (Backward Citations)
US3307168A
Cited
US3665445A
Cited
USPTO Annuity & Maintenance Windows
| Annuity Stage | Window Opens | Payment Deadline | Surcharge Period Until | Estimated Fee | Status |
|---|---|---|---|---|---|
| 3.5 Years (Year 4) | 1976-02-20 | 1976-08-21 | 1977-02-20 | $2000.00 | Window Closed / Lapsed |
| 7.5 Years (Year 8) | 1980-02-20 | 1980-08-21 | 1981-02-20 | $3760.00 | Window Closed / Lapsed |
| 11.5 Years (Year 12) | 1984-02-20 | 1984-08-21 | 1985-02-20 | $7700.00 | Window Closed / Lapsed |