Intrusion detection system
First Claim
1. An intrusion detection system for producing an alarm signal responsive to the repetition of a vibration-causing movement, comprising:
- a vibration sensor, connected to produce an output signal responsive to each occurrence of the vibration-causing movement;
timing means connected to establish a sensing window which is initiated upon the expiration of a predetermined delay time commenced by receipt of the first sensor output signal; and
a gate circuit, connected to be armed at the expiration of said delay time and to be triggered upon receipt of the first sensor output signal subsequent to the expiration of the predetermined delay time and prior to the expiration of said sensing window, thus producing the alarm signal only after the delay time has expired and at least one additional sensor output signal has been produced.
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Accused Products
Abstract
An intrusion detection system includes a vibration sensor, and a gate circuit operable to provide an output signal only after the vibration sensor produces a first signal, and thereafter a second, separate signal within a preassigned "sensing window" period. To accomplish this, a timer circuit initiated by the sensor determines a timing interval, and a delay circuit coupled to the timing circuit prevents switching of the gate circuit until preset delay time has elapsed. After the delayed time, if a second sensor output signal is received before expiration of the timing interval, the gate circuit switches and passes a signal through an integrated circuit amplifier stage, and a driver circuit to energize an output unit. The sensitivity of the vibration sensor can be adjusted. The integrated circuit stage includes circuitry for maintaining the alarm signal even if the system is switched to off after it goes into alarm. The same stage also checks periodically for a low battery condition, and provides an output warning signal if the battery level falls below a preset level.
32 Citations
14 Claims
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1. An intrusion detection system for producing an alarm signal responsive to the repetition of a vibration-causing movement, comprising:
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a vibration sensor, connected to produce an output signal responsive to each occurrence of the vibration-causing movement; timing means connected to establish a sensing window which is initiated upon the expiration of a predetermined delay time commenced by receipt of the first sensor output signal; and a gate circuit, connected to be armed at the expiration of said delay time and to be triggered upon receipt of the first sensor output signal subsequent to the expiration of the predetermined delay time and prior to the expiration of said sensing window, thus producing the alarm signal only after the delay time has expired and at least one additional sensor output signal has been produced. - View Dependent Claims (2, 3, 4, 5, 6, 7)
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8. An intrusion detection system for producing an alarm signal responsive to the repetition of a vibration-causing movement, comprising:
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a vibration sensor, connected to produce an output signal responsive to each occurrence of the vibration-causing movement; timing means, including a timer circuit coupled to the vibration sensor and operative, upon receipt of the first output signal from said sensor, to initiate a timing interval of preset duration, and further including a delay circuit, coupled to the timer circuit and operative, concomitantly with initiation of the timing interval, to initiate a predetermined delay time period shorter than the timing interval to establish a sensing window commencing with expiration of the delay time and ending with expiration of the timing interval; a gate circuit, connected to be armed at the expiration of said delay time and to be triggered upon receipt of the first sensor output signal subsequent to the expiration of the predetermined delay time and prior to the expiration of said sensing window, thus producing the alarm signal only providing at least one additional sensor output signal is produced during the period of the sensing window; and a transducer coupled to the gate circuit, for translating the alarm signal into a system output signal. - View Dependent Claims (9, 10, 11, 12, 13, 14)
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Specification