Classifications

• • G—PHYSICS
  • G08—SIGNALLING
  • G08B—SIGNALLING OR CALLING SYSTEMS; ORDER TELEGRAPHS; ALARM SYSTEMS
  • G08B29/00—Checking or monitoring of signalling or alarm systems; Prevention or correction of operating errors, e.g. preventing unauthorised operation
  • G08B29/18—Prevention or correction of operating errors
  • G08B29/183—Single detectors using dual technologies

Definitions

• the present invention relates to an electronic intrusion detection system for environments to be monitored.
• the invention is concerned with an electronic remote surveillance device adapted to be employed in combination with monitoring apparatuses, alarm systems, fire alarm devices, antitheft systems, etc.
• the volumetric sensors based on Doppler effect are substan ially small-size radar devices operating in the microwaves spectrum, typically 1-10 GHz, capable of detecting a person moving even at an extremely low speed.
• the infrared volumetric sensors are sensors capable of detecting a temperature difference caused by the passage of a human body in the environment in which the sensors are located, but these sensors cannot detect mechanical vibrations .
• volumetric sensors In presence of a body moving inside the environment or the space to be monitored, the above mentioned volumetric sensors generate an electric signal that can be applied to a control circuit that in turn actuates alarm warning devices or other devices that draw attention to the event by means of acoustic and/or optical (visual) alarm messages.
• a control circuit that in turn actuates alarm warning devices or other devices that draw attention to the event by means of acoustic and/or optical (visual) alarm messages.
• the acoustic and/or visual signal generated by the sensor ( s ) is converted into an alarm message and generally transmitted through a radio link or on a telephone line , either public or private , to a receiving device that can be located far away from the monitored place at which the event detection occurred .
• the alarm message can be sent either to a receiving device located in a central control unit manned by private personnel or by policemen , or to a f ixed or mobile telephone set , furnished to the surveillance personnel or even to the owner of a house .
• the alarm mes sage received through said devices can incorporate information relating to the place at which the event took place , such as for example a predetermined recorded vocal message .
• infrared sensors When infrared sensors are used in a monitoring system, many disturbing sources such as natural or artificial light sources, quick changes of temperature, e.g. caused by room convectors, sudden raise of the environment lighting due for example to the front lights of a passing car, are all capable of being detected by the sensors and generating (false) alarm signals. Moreover, the sensibility of infrared sensors decreases when the environment temperature increases .
• the alarm message received at the remote location does not contain information allowing the, personnnel in charge to decide with certainty whether it is due to a real or a false alarm
• such monitoring systems suffer from several drawbacks, such as delayed interventions, or unnecessary interventions, with a reduction of the system reliability.
• the owner of a dwelling that is far from home has to decide whether to ask for an intervention, or inform the police, or simply disregard the message as a false alarm, only on the base of a generic alarm message he/she has received.
• One of the suggestions was to adjust the threshold level of the sensors to different conditions of the environment disturbances , another provided for pulse counters that actuated an alarm signal only after receiving a predetermined number the sensor detections , more likely to be caused by the presence of an intruder moving within the protected enclosure .
• Still another device provided for using a combination of Doppler and infrared sensors both of which had to be activated before an alarm message was generated.
• FR-A-2 611 290 One of such devices is disclosed in FR-A-2 611 290 concerning an alarm device capable of transmitting an alarm message.
• the device illustraed and described in FR-A-2 611 290 comprises a volumetric sensor that upon being activated actuates a telephone dialing device the emits a predetermined stored number and transmits an alarm message through a telephone line.
• an environment hearing is started through a microphone that allows the remote listening of the sounds and noises within the monitored space .
• the remote listening through microphones requires the installation of additional devices in the rooms to be monitored and does not allow the listening of low intensity noises, such as those caused by slow movements.
• a further object of the present invention is to realize an intrusion detection system that is both reliable and easy and inexpensive to install and to use. Disclosure of the Invention
• the system generally comprises a number of volumetric sensors la, lb, lc that can be positioned in the environmen (s ) to be monitored in accordance with different patterns, such as one sensor for each room or two or more properly arranged sensors inside each (or a single) room to be monitored to increase the area kept under surveillance, in accordance with known techniques .
• the volumetric sensors la, lb and lc can be either infrared sensors or sensors detecting the frequency shift caused by Doppler effect, hereinafter referred to as Doppler sensors.
• infrared sensors When a human body passes through their detection range, infrared sensors generates a change in their output voltage signal, whereas Doppler sensors generates a frequency change in the reflected signal (generated by a not shown source) that is proportional to the speed and to the direction of the movement.
• each node 3a, 3b, 3c is connected both to the input of an alarm generating circuit 10a, 10b and 10c, enclosed in a dashed box in the Figure , and to the input of a transducer or conversion circuit 20a, 20b and 20c, enclosed in a dash-and- point box in the Figure .
• Each of the alarm circuits 10a, 10b and 10c outputs an alarm signal ALARM having a suitable voltage level when a predetermined alarm condition is met.
• each of the alarm circuits 10a, 10b and 10c comprises a threshold detector (11a, lib, lie) connected a trigger circuit (12a, 12b, 12c) that actuates a relay (13a, 13b, 13c) or similar device that generates the alarm signal.
• the corresponding relay 13a (13b, 13c) that is actuated by the trigger circuit 12a (12b, 12c) driven by the threshold detector 11a (lib, lie) supplies the alarm signal from said alarm circuit 10a (10b, 10c) .
• the corresponding relay 13a, 13b and 13c switches from a rest condition to an alarm condition and enables an alarm signal or message to the transmitted to the respective alarm input 31a, 31b, 31c of an alarm control unit 30 through an alarm signal transmission line 14a, 14b, 14c.
• a multiplexer or switch 32 provided in the alarm control unit 30, receives an ALARM signal having a proper logic level, e.g. 5 V for indicating a logic one, and about 0 V for indicating a logic zero, this signal representing the state of the sensor la or lb or lc that generated the alarm signal.
• the conversion or transducer circuit 20a, 20b and 20c comprises a voltage controlled oscillator or VCO 21a, 21b, 21c respectively, whose oscillation range is maintained in the (audio) frequency band from 300 Hz to 3,000 Hz corresponding to the telephone speech band, and a modulating circuit 22a, 22b, 22c respectively.
• the amplified signal from the volumetric sensor la (lb, lc) is used to drive the voltage controlled oscillator or VCO 21a (21b, 21c) and the output audio -frequency signal from the VCO is modulated in a modulating circuit 22a (22b, 22c) before being transmitted, on a transmission line for audio signals 23a (23b, 23c) , to a demodulator 33a (33b, 33c) provided in the control unit 30.
• any modification of the electric output from the sensors la, lb, lc is continuously converted into an audio signal, i.e. a signal that can be perceived (in the present case, heard) by a human being.
• This audible signal is correlated with the monitored environment, i.e. contains information about what ' s happening within the monitored space .
• this audible signal is a sort of "audio" picture of the thermal pattern changing in the monitored space .
• the sensors are Doppler sensors, this audible signal "represents" the motions occurring within the monitored space. In both cases the listener can easily distinguish the audio signals caused by an intrusion from those caused by disturbances, such as temporary phenomena or periodic sounds such as those produced by a banging door.
• the output (audio) signal from demodulator 33a, 33b, 33c is applied to a corresponding input channels 34 of the multiplexer 32 the output of which is connected to an audio amplifier 40.
• Each of the input channels 34 to the multiplexer 32 can be enabled to reach the audio amplifier 40 by a logic address fed to one of the addressing inputs 35 of the multiplexer 32, connected to the outputs of the relay 13a, 13b, 13c, respectively .
• the multiplexer 32 Through the multiplexer 32, one or more of the multiplexed audio signals are applied to the audio amplifier 40 the output of which feeds a telephone dialing device 41
• the audio signals signal can be received by any selected telephone set 42 or equivalent receiving device available to the surveillance personnel .
• the alarm signal ALARM activates the telephone dialing device 41 for the setting up the connection with the receiving telephone set 42, and then the same signal enables the transmission along the telephone line 43 of an audio signal that is proportional to the activity detected by the volumetric sensor la, lb, lc .
• the above audio signal can be directly applied to a (not shown) loudspeaker disposed in the audible range of the surveillance personnel, such as for example the caretaker of a museum or other premises .
• each signal generated by the volumetric sensors is converted into a form adapted to drive a display visible to the surveillance personnel, such as a CRT monitor, e.g. connected to the other end of the telephone line 43 and capable of visually representing the movements taking place in the monitored space, e.g. by changing the images shown.
• a display visible to the surveillance personnel such as a CRT monitor, e.g. connected to the other end of the telephone line 43 and capable of visually representing the movements taking place in the monitored space, e.g. by changing the images shown.
• the watcher could get a graphic representation of the movements occurring in the monitored space.
• Such representation is not the visual display of a television camera, but is nevertheless capable of allowing an easy and positive discrimination between an intrusion and other phenomena.
• the signal generated by the volumetric (Doppler or infrared) sensor la is directly applied to the relay 13a (13b, 13c) which relay is generally incorporated in the same housing of the sensor.
• This embodiment is schematically shown in Fig. 1 by the dashed line connection between the output of amplifier 2a (2b, 2c) and the relay.
• the so obtaind pulse signal has a period that is proportional to the relay opening/closing cycle, and therefore is representative of the detection activity of the volumetric sensor, but is more "clean" (that is contains less spurious signals) in respect of a signal directly coming from the sensor.
• the above embodiment of the invention has further the advantage of a simpler construction since the transmission line 14a, 14b, 14c - provided for sending the ALARM signal - can be used also for transmitting the signal from the unit containing the volumetric sensor and the relay to the alarm control unit 30.
• the analysis for detecting when the threshold has been exceeded i.e. an alarm condition
• the relays 13a, 13b, 13c are advantageously formed by solid state relays that are more suitable to be continuously closed and opened at a high rate.
• the signal transmitted on audio transmission line 23a (23b, 23c) to the control unit 30 is continuously stored in a memory device provided for in this unit.
• a memory device is a solid state memory capable of continuously storing an interval or "frame" of the signal.
• unit 30 will contain a plurality of memory devices, each one for storing the signal from one of the sensors located in the monitored environment .
• the stored signal can be transmitted along the telephone line to the surveillance personnel immediately after the trasmission of an ALARM signal that has warned the personnel of a possible alarm condition. Since the signal that caused the alarm has been stored, the surveillance personnel will have the additional possibility of listening to the signal - converted into audible form - that caused the alarm. However, once the stored signal has been transmitted, the system will start to transmit the current or real time signal so that the personnel can monitor what is happening in the monitored environment .
• the movements can be displayed even without triggering any alerting signal, by sequentially enabling the channels of multiplexer 32, either manually or electronically.
• the invention is applicable in the field of the alarm and antitheft systems for protecting civil dwellings and industrial premises from intrusion through a remote surveillance .

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• Engineering & Computer Science (AREA)
• Computer Security & Cryptography (AREA)
• Physics & Mathematics (AREA)
• General Physics & Mathematics (AREA)
• Burglar Alarm Systems (AREA)
• Alarm Systems (AREA)
• Investigating Or Analyzing Materials By The Use Of Fluid Adsorption Or Reactions (AREA)
• Paints Or Removers (AREA)
• Emergency Alarm Devices (AREA)
• Cable Accessories (AREA)

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Citations (2)

• 1996
  • 1996-12-24 IT IT96TO001080A patent/IT1289800B1/it active IP Right Grant
• 1997
  • 1997-07-30 AU AU38500/97A patent/AU727852B2/en not_active Expired
  • 1997-07-30 HU HU9902390A patent/HU222942B1/hu active IP Right Grant
  • 1997-07-30 AT AT97935552T patent/ATE223606T1/de active
  • 1997-07-30 PL PL97328502A patent/PL184165B1/pl unknown
  • 1997-07-30 DE DE69715183T patent/DE69715183D1/de not_active Expired - Lifetime
  • 1997-07-30 CZ CZ19982688A patent/CZ293095B6/cs not_active IP Right Cessation
  • 1997-07-30 WO PCT/EP1997/004142 patent/WO1998028724A1/en not_active Ceased
  • 1997-07-30 EP EP97935552A patent/EP0898771B1/en not_active Expired - Lifetime
  • 1997-07-30 CA CA002242870A patent/CA2242870C/en not_active Expired - Lifetime
  • 1997-08-06 ZA ZA976988A patent/ZA976988B/xx unknown

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