GB2391674A - Distance monitoring system with optional signal boost to extend range - Google Patents

Abstract

A distance monitoring system has a monitor and a tag, both of which contain a radio transmitter and receiver such that an alarm on the monitor can be activated if the radio signal strength indicates that the distance between the tag and the monitor exceeds a preset distance. The signal strength can then be boosted to allow communications to continue. An alarm on the tag may be sounded either automatically or by the user.

Description

r 1 2391 674 Tag Monitoring: System l his invention relates to a tag

monitoring system, and particularly to a tag monitoring system for monitoring the separation of twit items, people and/or the like due to theft, accidental loss fir misplacement.

lathe theft of small portable articles of value, such as mobile phones, wallets, purses and laptop computers, is becoming increasingly common. The theft of a valuable item can cause distress to the owner and expense to either the owner and/or insurance companies who have to honour insurance claims. In addition to theft, it is common for people to, misplace or lose valuable items and it can be time consuming and frustrating for the user when trying to locate the misplaced item or items.

In an attempt to overcome the above problems, it is known to attach valuable items via a wire or chain to the owner. This may To inconvenient to the owner, detract aesthetically from the appcarancc off the item or owner and may restrict the owner's use or operation of the item. US5512877, US4899135 and (3132335774 disclose the concept of using a monitoring crevice to detect when an associated tag device is moved beyond a pre-

cletermincd radius from the monitoring device. The monitoring and tag crevices can communicate with each other by a variety of differcot types of known communicatic>n techniques, such as RF radio frequency waves, infra-red, ultra-sonics. lathe monitoring device detects whether there is a signal present from the tag device and the strength of this received signal. If the signal strength diminishes bek>w a threshold level, then the monitoring device activates an alarm locally or elsewhere to indicate that the tag dcvicc, anal more importantly the article to which the tag device is attached, is outside the allowed perimeter.

In US5512877, which specifically relates to a method of preventing removal of a baby from a hospital, a plurality of fixed rcccivc..rs are required to he provided at spaced locations in the hospital, thereby resulting in the monitoring device being expensive and making it impractical for use outside of large institutions, such as hospitals. In addition, whilst this method and the methods in US4899135 and CJB2335774 inform the relevant auth'rities/pcrson that a baby has been taken, it does not provide any further information other than the event has occurred. Furthcrmore, the monitoring devices are likely t, be used in busy, noisy environments, with other forms of communication apparatus and devices being present which might interfere with the communication of the signal from the tag device to the monitoring device. ( onvcotional methods are therefore >f limited use only.

lthc aim of the present invention is to provide an improved tag monitoring system which overcomes the abovementioned roblcms. iNcccrding tc> a first aspect of the present invention there is provided a tag monitoring system including a monitoring device and a tag device, each of which is provided with signal receiving and transmitting means, said monitoring device and said tag device being capable of remotely communicating with each other cover a pre-dctcrminecl range using airboroc signals transmitted and received by said signal receiving and transmitting means, at least said monitoring device also including signal strength detection means and alarm means, the function of the system being try trigger the alarm means of at least the monitoring device when the signal strength reduces brow a threshold value of the signal strength detection means, thereby indicating that the tag device is distant from the monitoring device by more than a prc-determincd distance, and wherein at least one of said

l I ( monitoring device and said tag device further includes selectively opt table signal boost means which amplify the transmitted signal above its normal intensity, such that a tag device disposed remotely from the monitoring device by a distance greater than said prc-detcrmined distance can receive said amplified boost signal.

According to a second aspect of the present invention there is provided a tag monitoring system including a monitoring device and a tag device, each of which is provided with signal receiving and transmitting means, said monitoring device and said tag device being capable of remotely communicating with each other over a pre-dctermined range using airlorne signals transmitted and received by said signal receiving and transmitting means, and wherein the tag device communicates with the monitoring device by transmitting at least two signals representative of substantially identical information and being spaced from one another in time and/or frequency, said monitoring device being provided with circuitry capable of detecting said at least two signals and decoding the same to identify when said tag device is within a pre-determincd distance of the monitoring device.

l'referably the monitoring device also includes signal strength detccti'n means and alarm means, the function of the system being to trigger the alarm means of the monitoring device when the strength of the field transmitted by the tag device and

received by the monitoring device reduces below a threshold value calf the signal strength detection means, thereby indicating that tht tag device is distant from the monitoring device by more than a pre- dctermined distance.

l'hus the present invention allows the tag monitoring device to work river a short distance range, in addition to a longer distance range, to provide alarm activation following theft or

loss of an item or person and a method of retrieving an article respectively, and the facility for transmitting two signals either simultaneously and of different frequencies, or one after another and of the same frequencies allows the monitoring device to effectively determine when the tag device transgresses a prcdetcrmincd boundary.

l'refcrably the tag device is additionally provided with signal boost means.

l'rcferably the monitoring levicc is provided with a retrieval mode, which is activated either automatically following a prc-

detcrmined event occurring in the system or following manual actuation by a user. In the retrieval mode a signal is transmitted from the monitoring device to the tag device which activates alarm means in the tag device. thus the user is typically able to hear the tag device and establish the location of the tag device and also the item or person to which the device is attached.

I'rcfcrably the retrieval mode is activated substantially simultaneously on receipt of a signal falling below said threshold level. Preferably the retrieval mode has a range of approximately 15 metros. This range is greater than the prc-determincd threshold distance provided for the monitoring mode (i.e., monitoring of the signal strength from the tag device by the monitoring device). Preferably a button or switch is provided to allow a user to manually activate the retrieval mode. The button or switch can be actuated periodically or continuously to provide a continuous, single ancl/or periodic audible alarm in the tag device.

I! In a further aspect of the present invention, the selectively operable boost signal is claimed in the tag monitoring system

without the function of the signal strength detection means, thereby in effect, allowing the system tc> be used as a retrieval system only.

In one embodiment, the signal boost means are typically disabled in the mc>nitoring device at pre-determined time intervals, thereby allowing the monitoring unit to sample and detect tag device signals in order to determine whether the tag device is within a pre-determined distance from the monitoring device, without boosting of the signal. The signal boost means in the monitoring device is disabled for only a limited period of time before being enabled again.

Preferably the signal boost means are in the form of an autc>matic gain control (AC,(). The AG(, allows signals passing between the tag and monitoring devices to be sampled even in lousy envirc>nments or where there are potential obstructions, thereby preventing degradation of the signal as a result of interference. As such, the alarm means, is not activated every time there is an accidental disruption of the signal between the devices. Preferably the monitor and tag units communicate by the transmission of two substantially identical RF encoded data packets transmitted at different frequencies on different channels. For example, the two different frequencies can be 433.92Kh% and 433.95Khz. al he provision of two synchronised data signals allows the units to distinguish between received signals (i.e., signals sent from the Other unit) and reflected/scattered signals which have been reflected off oh jccts, other people, buildings and/or the like.

Preferably each signal transmitted between the units is provided with identification means and are typically in sequence.

(Counting or timing means provided in the unit or units detects the order of the received signals and signals sent out of sequence, due to the signals being scattered or reflected, are disregarded by processing means in the relevant receiving unit.

Since twc substantially identical signals are sent at different frequencies, the likelihood of obstruction or corruption of both of these signals, when the tag and monitoring unit are within a pre-dctermined range of each other, is greatly reduced. This reduces the likelihood of accidental activation of the alarm in the monitoring or tag units in busy or RE noisy environments.

Preferably the AC1 (, functions in combination with a dynamic range log detector and a compound data slicer. Preferably these are locked onto the signal strength detection means and timing means, thereby providing the system with an accurate <operational range (deteeti<'n range).

Preferably the A(]C further functions in combination with comparison means (typically in the form of a comparator integrated circuit (I.C)) for comparing the at least two received R1; encoded data packets. Each packet of data is synehronised on two channels, and the comparison means compares the received signals to check for corruption, whether the received signals are out of phase and/or the like.

Inferably timing means are provided in the tag monitoring system to allow the signal data passing between the tag and monitoring devices to be sampled at pre-determined time intervals.

Preferably the timing means is in the form of timing logic provided in the circuitry of said monitoring and/or tag devices.

I'rcfcrably the tag and monitoring devices communicate via radio waves (radio frequency (RI-')).

:\ threshold limit can be pre-set for the signal strength detection means by the user or manufacturer, the threshold signal strength value corresponding to a pre-determincd separation distance of the tag and monitoring devices beyond which the alarm means is activated. l'referably the signal strength detection means operates over a default distance of 34 metres, such that when the tag and monitoring devices are separated I'y more than 3-4 metros, the alarm means is activated.

The alarm means can be any or any combination of an audio, visual fir kinaesthetic alarm, such as an audible sound(s), one or more flashing lights or symbols and/or text for display on a control panel display, vibrations and/or the like.

Preferably each of the monitoring and tag devices are provided with on/off switches to move the devices between Operational and ncn- operational conditions.

l'hc tag and monitoring devices can be secured to an article or person via any or any combination calf conventional securing means, such as adhesive, clips, nut and bolt, VELCRO, integrally formed with an article, stitched into fabric of an article or clothing, as part of a smart card, SIM card or other memory card, attached via a key ring, kept in a pocket car clothing or compartment of an article and/or the like.

PrcEcrably a tamper proof sensor is provided on either or both elf the monitoring and tag devices, such that if an attempt is made to physically remove a device from an item to which it is so cured, a warning signalling, typically an audible alarm is generated in cane or both of the dcviccs.

In one embodiment the tag crevice is located on an article of value and the monitoring crevice is located with a user, who is typically the owner of the article of value.

I:urthet aspects of the present invention which are independently and separable claimed are in respect of the monitoring device and the tag device, and method of operation of the tag monitoring system.

The present invention can be used on any item of value which allows a tag device to bc located thereon or therein, and which is typically portable, such as a mobile tclcphone, laptop computer, handbag, purse/wallet, camcorder, camera or other portable electronic equipmcut, keys and/or the like. I'he present invention therefore allows a user to be informed of when a valuable item is stolen or accidentally dropped, provide a means of retrieving a valuable item which may have been misplaced or stolen and provides a means of preventing or at least reducing the incident of accidental activation of the alarm means in the tag monitoring system due to signal interfere nce between the tag and monitoring devices.

fin embodiment of the present invention will now be described with rcfcrcoce to the accompanying figures whcrcin: I;igurc I illustrates an example of a monitoring device according to an embodiment of the prcscut invention;

( Figure 2\ illustrates an example of the front of a tag device accorcling to an cmbodimcot off the present invention; Figure 213 illustrates the rear of the tag device shown in Figure 2A; leisure 3 is a schematic representation of the tag monitoring devices; ligurc 4 is a schematic representation of a transceiver in the monitoring device; and Eigurc 5 is a circuit diagram of signal strength detection means.

In accordance with the present invention there is provided a tag monitoring system, hcrcinaftcr referred to as a ValueMindcr'M, comprising a monitor module (MM) 102 and a tag device in the form of a controllcrm'dulc ((-M) 140. In use, the controller 140 is l'catcd on an item of value belonging to a user, such as a mobile telephone, anal the user has the monitor 102 in their possession. The monitor 102 and controller 140 communicate with each other using RF cncodccl digital signal data as hereinafter dcscrilcl. 'lathe encoded nature of the data provides the controller and the monitor with unique addresses, thereby preventing other signal data from being intcrccptcd by either unfit. lathe monitor 102 comprises a transceiver 103 for receiving and transmitting signal data, a signal field strength monitor (E;'SM)

106, comparison means in the form Off a comparator integrated circuit (I. (2) a digital encoder/decoder 108, an audio/optical alarm 110 and control circuitry 104, as shown in Figure 3. A digitally encoded RF signal received by the monitor unit 102 is

first passed via an aerial to an input filter and then to the FSM, the comparison means 105 and digital decoder 108.

lithe components of monitor 102 ate located in a housing 3, as shown in figure 1. The housing 3 is provided with two buttons; a retrieve button 6 which allows a retrieval mode of the controller 140 to be actuate<1 following depression thereof, and a button 8 fair switching the monitor to an operational condition and resetting the operational status of the unit.

lhc monitor housing 3 is also provided with a speaker 10 for sounding audible alarm 110 and an LED 4 for the visual LED alarm 110. An aperture 12 is provided in housing 3 to allow the monitor to be attached to a user's keyring, belt and/or similar.

\ compartment (not shown) is provided in housing 3 for the location <>f batteries used to power the unit.

I'he controller 140 comprises a transceiver 141 for receiving and transmitting signal data to and from the monitor unit, a digital encoder/decoder 142, an audible alarm 144 and control circuitry 146, as shown in figure 3.

I'hc componcots of controller 140 are located in h<,using 43, having a front face 42 and a rear face 48, as shown in figures 2a and 2b. speaker 44 is provided on front face 44 for sounding of alarm 144. A compartment 46 is provided in housing 43 for the location of batteries used to power the unit.

I\ contact sensor 50 is provided on the rear face 48 of housing 43 which acts as a tamper proof alarm, such that if an attempt is made to remove the controller from the item of value, the alarm in the controller and/'r monitor is activated.

Operation. Functions & [features

1 1 [Switch ()nl When the ValueMindcr is switched on both the Monitor module (?vIM) and the ( ontroller module ((M) beep once to indicate..

that they are active and communicating.

[Normal Usc When a valuable (with a ValueMinder ( ontroller Module attached) is within the detection range (DR) of 3 to 4 mctres (1()-15ft) no action is taken.

[Mislaid Valuablel If there arc no beeps at switch on, the valuable has probably been mislaid.

\ valuable which has been mislaid in the home, office or a car, for example, can be located by using a retrieve mode or "burst signal mode". The burst signal mode has a range of up to 15 r metros and can be used to detect mislaid valuables within that range. I l he "R" retrieve button activates the burst signal mode and should be pressed once every 2 to 5 seconds. If the (,M beeps: but the valuable cannot be seen, the user continues to press the "11" button at 2 to 5 second intervals until the valuable is found.

When the valuable, with the CM attached, is within the normal DR (3 tr, 4 metres) the (,M and the MM will both beep once to confirm that they arc communicating.

lA ttemp ted Theft If the valuable is taken beyond the DR (detection range) the MM will alert the owner to this fact by an audible alarm and by the flashing of a light emitting diode.

The alarm will automatically stop and the system will reset if the valuable is brought back into the DR. If the valuable is not brought back into the detection range and if the "R" retrieve button is pressed, a burst signal will be transmitted to the CM.

l'hc (,M, which is attached to the valuable, will immediately sound out an alarm. Consequently the owner will be able to pinpoint any person who may have stolen the valuable.

I f the Monitor Module (which is usually kept on the person or on a key ring) is taken beyond the DR the MM will sound an audible alarm immediately and after 5 seconds the CM alarm will also ring out from the valuable. 'l'hc alarms will automatically stop and the system will reset if the (,M and the MM arc brought back into the I)R.

[Out Of Lange Controllerl If the valuable is accidentally or deliberately moved beyond the I)R the MM will alert the owner by an audible alarm and optical means. I()ut Of Range Monitor] If the MM is either accidentally or deliberately moved beyond the DR the MM will sound an audible alarm and after 5 seconds the (,M alarm will sound from the valuable.

['lampcr Protection] If the (,M is tampered with or if it is removed from the valuable the tamper proof sensor will trip the Controller Module alarm.

Technical Description

[Overview |

The ValueMinder consists of two modules, known as the l\Ionitor Module and the (,ontrollcr Module as described above.

lhc ValueMincier Complies and functions within the unlicensed nominal radio frequency band of 434MHz.

l'lthe Mcnitcr Modulel the Mcnitc>r Module comprises of a'lranseeiver, signal strength letcetic>n means in the form of a Field Strength Monitor (FSM),

a digital encoder /deeotler, a control unit, a Comparator and an audio / optical alarm system.

l-he Monitor Module is responsible for receiving and processing the data from the (controller Module and has a nominal operating range (detection range) of 3 to 4 metres. In the burst signal encode, the range increases to approximately 15 metros.

l'he Monitor Module is housed within a small box which is kept can the person.

where are two buttons for user operation which have been previously cleseriLed.

fit switch on the Monitor Module transmitter, with a power output calf 300miero watts l.RP (effective radiated power), sends cut a unique Code to the (controller Moclule.

I'he (,ontrc>ller Module has to respond within 100ms. If a response is received within the time limit the system initialises.

:\ digitally encoded RI: signal from the CM is first passed via the aerial to the input filter and Field Strength Monitor and then

canto the MM receiver, the comparator and the digital decoder.

If the ISM detects a sufficient field strength and the decoded

information is correct and the receive window timing (30ms) are all synchronised then no action is taken.

If the (1;) field strength falls below the 1i't; threshold, or if the

digital code becomes corrupted (due to leek of signal) the Monitor Module will note the condition change and turn on the alarm circuits.

When communication is re-established the alarm will cease and the system will re-initialise, automatically. '1'he alarm can be muted lay pressing and holding down the "S'7 set button for five second s.

\ "burst signal' high output mode is provided within the Monitor NIcdule. 'lithe burst signal mode is activated by pressing the "11" retrieve button. If the lutist signal mode is engaged the Monitor Module powers up the on board transmitter into high a output mode of 2 milk watts F,111'7 and simultaneously sends the C ontroller Module an encoded data signal which forces the (<>ntroller Module to trip into alarm mode.

lthe burst signal high output mode is capable of transmitting over distances of up to 15 metres. 'the burst signal high output mode is activated only when the retrieve button is pressed down and held for at least 2 seconds.

lThe Controller Modulel lithe (controller Module has two variants. Version Si (serial) comprises of a control unit, a transceiver, a digital encoder / decoder and an audio alarm indicating system. Version P (parallel) comprises of a control unit, two transmitters, a receiver, a digital encoder / ciecoder and an audio alarm indicating system.

l The output power of the individual on board transmitters are rated at 300 micro watts TARP which produces an operating range of 3 to 4 metres. lhc (-ontrollcr Module attaches to the valuable and is responsible for transmitting encoded data to the Monitor Module. Lila (controller Module listens for a digitally encoded Rli signal from the MM. If no signal is received the CM remains in "stand lay listening mode', to conserve battery power. If a "wake up" signal is received the ( M will first, via the aerial, input filter and receiver pass the signal to the ligital rlccodcr for verification.

When the (,M has been initialiscd the ( M will send the MM, every two seconds: (for tl'hc Serial, Economy Version) 25ms llE; signal which contains two consecutive digitally encoded data packets. The lata packets are identical. The first data packet is transmitted immediately and the second data packet follows 1 5ms latter. If either of the data packets are received by the MM, within the receive window timing (30ms), no action is taken.

l'he purpose of the delay between the transmitted data packets is to reduce the probability Off false alarms due to multipath signals and signal fade.

(I-or'l'he Parallel Version) \ two channel, simultaneous 25ms RI. signal each c, f which contains one digitally encoded data packet. '[he data packets are idcotical. If either one or both of the data packets are received by the I\IM within the receive window timing (30ms) no action is taken. 'I'he simultaneous transmission of two identical data packets on separate frequencies (channels) and consequently on

two different wavelengths greatly reduce the probability of false alarms due to multipath signals and signal fade.

If at anytime the ( ontroller Mcdule receives a burst signal instruction from the Monitor Module the (,M gives priority to that instruction.

hc ( ontroller Module transmitter circuitry is temporarily powered down and an alarm will be sounded from the CM. On removal of the burst signal the ValucMinder will automatically reinitialisc and attempt to resume communication.

I tJ niquc to the ValueMinlcrl \t the heart of the ValueMinder is the FtSM, two OC)K (on/off/keyed) Transceivers (three for the parallel version), two Digital 1 ncoders and Decoders, a Timer / Counter, a (comparator and three alarm indicators, two audio and one optical. ValueMinder Sc F8Mi (Background and Function)

l he I;SM is in its self a receiver with the following properties.

\ selective tuned front end receiver, a detector, an operational amplifier data slicer and an analogue to digital converter functioning as a dynamic logarithmic detector.

rIhc AM is sensitive to the near field strength and thermal fade

margin of the ( ontroller Module transmitter. As the fiekls begin to weaken, (when the ValueMinder modules arc about 3 metres apart) the F8M will detect the change and force the MM Receiver to disable the AG(_. As the fields further deteriorate (at

almost 4 metros) and to ensure that a fault condition occurs the 1;SM disables the decoder verification process which will then trip the Monitor Module into the alarm mode.

Conversely as the fields return the FSM re-enables the AGC and

the decoder verification process.

l'he system will re-initialise and then revert to normal operation.

1-' avoid interference from other ValueMinders the Monitor N,I()dUIC7 the F5M, and the Controller Module are sensitive only t' their respective synchronised and specific encoded data packets. Radio waves are scattered by the human body and thus some of the scattered waves will travel back toward the receiver. An ordinary receiver responds to the sum of the incident (desired) and the scattered (reflected) waves. The phase of a scattered wave and the phase of an incident wave differ. The intrinsic phase shift of the scattered wave is due to the electrical properties of the body. The other phase difference is the result of the scattered (reflected) waves travailing different distances to the incident (lesired) waves. The ValucMinder is not affected by reflected or late signals as any data packets contained in the scattered waves will be out of sequence and consequently cliscardcd. In an ordinary receiver, loss of signal occurs when the scattered (reflected) waves destructively interfere with the incident (clesired) waves. 'lathe ValueMinder is not affected by a loss of signal due to destructive interference in the same way as an ordinary receiver.

Because the V alueMinder CM (parallel version) transmits an identical synchronised data packet on two different frequencies and hence two different wavelengths, the propagation of each wavelength will have different wave scatter characteristics.

Unwanted wave scatter interference is thus kept to a minimum.

In the case of the VauleMinder CM (serial version) two identical data} rackets are consecutively transmitted on the same frequency but with a delay of 1 5ms in between each packet.

tWincc wave scatter characteristics vary with time and surroundings, the delayed serial transmission overcomes most calf the unwanted scatter effects.

loo operate successfully the ValueMinder MM requires only one intact data packet in each reccivc window timing of 30ms from clthcr version.

If any of the data packets, received by the Monitor Module, arc not on time or they are not in synchronisation or they are not in sequence the MM will then transmit a reset code tc> the Control M>dule once every 30ms for a period of 90ms. If the CM responds within 30ms no action is taken, but if the CM fails to respond within the given time limit the MM will trigger the alarm system.

When the transmitted encoded data packets, from the C:M, are rcccivccl bythe MM each data packet is first processed by the 1;811 and the MM rcccivcr. Any received data packet is then compared with a preset binary refcrcncc pattern, which is held in the decocler. If the comparator accepts that the received data packet is on time, in sequence and matches the preset reference pattern the data packet is then passed on to the decoder. When the encoded data packet (s) has / have been decoded (verified) by the decoder, and if the received data packet (s) is / are identical to the rcfcrcncc pattern the decoder will send a re-

enable signal (acknowledgement) to the comparator.

al hcrcfc>rc, if either of the received data packets or both of the received data packets arc on time, in synchronization, in scqucocc and identical to the reference pattern, no action is

taken. 'l'hc system counter is updated, the count is incremented by one, and the comparator is reset (flushed).

I f, in any scqucnce, the received data packets are not in synchr'nisation, not received within the time allowed' corrupted or otherwise, even after a rc-try / reset the Monitor Module defaults to the alarm mode.

ids mentioned above, the ValucMindcr is available in two versions: l'arallcl Version' which operates with two simultaneously transmitted, parallel, sequential and synchroniscd encoded data packets, each of which are independent but identical. The encoded data packets arc simultaneously transmitted on twc> channels. Each channel has a slightly different wavelength and hence a different reflected (scatter) wave characteristic.

Serial Version, which operates with two sequential and identical encoded data packets each of which are transmitted serially in synchroniscd groups of two. 'I'hc encoded data packets are sctlucntially transmitted on a single channel. teach encoded data packet in any one group is spaced by a time delay and hence a different reflected (scatter) wave characteristic will result for each packet.

I'hc design features of the ValucMindcr (the mode of transmission, the mode of rcccption, the ISM and the logic control) satisfactorily contribute try the control of the desired (incident) wave and the field strength while reducing

interfcrcncc from the unwanted scattered (reflected) wave.

l'hc ValueMinder can be attached t, any suitable article. In one embodiment the Valueminder is attached to a laptop computer by mounting the tag devicc/(:M circuitry within a PCMCIA

( (hard. 'lhus, by the using the standard PCMCIA interface protocols, it is possible to provide a laptop computer with added protection against theft car loss.

The function and detection of the ValucMinder will be controlled by a software programme which will reside in the boot sector of the internal laptop hard drive. On start up of the system, the software looks' for the ValueMinder. If the ValueMinder P(,MCCIA Card is inserted and the MM is within range, the computer will boot up. If the P(:M(Iil Card is not inserted the laptop computer will not boot up. If the P(,MCIA (,arcl is removed during or after boot up the computer will shut down. In the event that a person attempts to delete the boot sector software from the computer, an alarm is sounded from the P(M(;IA (,ard and MM. The other functions of the ValucMinder operate in a similar manner to the above described embodiments. [thus it can be seen from the above description that the present

invention provides an improved tag monitoring system which has greater use, is smaller, more compact and is inexpensive ccmparcd to conventional monitoring devices.

Claims (1)

1. ( [aims: 1.;\ tag monitoring system including a monitoring device and a

   tag device, each of which is provided with signal receiving and transmitting means, said monitoring device and sai<l tag device being capable of remotely communicating with each other cover a pre-determined range using airborne signals transmitted and received by said signal receiving and transmitting means, at least said monitoring device also including signal strength detection means and alarm means, the function of the system being to trigger the alarm means of at Ieast the monitoring device when the signal strength reduces below a thtcshold value of the signal strength detection means, thereby indicating that the tag device is distant from the monitoring device by; more than a pre-determined distance, and wherein at Ieast one of said monitoring device and said tag device further includes selectively cpcrable signal boost means which amplify the transmitted signal above its normal intensity, i such that a tag device disposed remotely from the monitoring <Ievice by a distance greater than said pro determined distance can receive said amplified Taoist signal.

   2. A tag monitoring system according to claim 1 wherein the tag device communicates with the monitoring device by transmitting at least two signal representative of substantially iclentical information and being spaced from one another in time and/cr frequency.

   3. A tag monitoring system according to claim 2 wherein the monitoring Ievice is provided with circuitry capable of detecting said at Ieast two signals and decoding the same to identify when said tag device is within a pre-determined distance of said monitoring device.

   4. I\ tag monitoring system according to claim 1 wherein the monitoring device is provided with a retrieval mole, in which at least one signal is transmitted from the monitoring device to the tag device which activates alarm means in said tag device.

   5.;\ tag monitoring system according to claim 4 wherein the retrieval mode is activated automatically following a pre-

   dctermined event.

   6. iX tag monitoring system according to claim 4 wherein the retrieval mode is activated manually by a user.

   7. \ tag monitoring system according to claim 5 wherein the i retrieval mode is activated substantially simultaneously on receipt off a signal falling below said threshold level.

   8. \ tag monitoring system according to any preceding claim wherein the signal range of the tag and monitoring devices in the retrieval molly is greater than the pre-determincd threshold distance at which the alarm means is triggered.

   9. A tag monitoring system according tc' any preceding claim 6 wherein a button or switch is provided to manually activate the retrieval mode.

   10. A tag monitoring system according to claim I wherein the signal boost means is in the form of an automatic gain control (AGC).

   11. A tag monitoring system according to claim 1 wherein the signals transmitted between the tag device and monitoring

   cIcvice arc provided with idcotification mean and are in sequence 12. \ tag monitoring system according to claim 11 wherein counting or timing means provided in the tag device and/or monitoring device detect the sequcoce order of the signals via the identification means.

   13. A tag monitoring system according to claim 10 wherein the GIG ( functions in combination with a dynamic range log detector and a compound data slicer.

   14. \ tag monitoring system according t, any preceding claim wherein the AG C, dynamic range log detector and compound data slicer lock onto the signal strength detection means and timing means to provide the system with a signal detection ranc.

   15. tag monitoring system according to any preceding claim wherein the ACC functions in combination with comparison means for comparing the at least two received substantially identical signals.

   16.A tag monitoring system according try any preceding claim wherein the tag device and/or monitoring device is provided with timing means to allow the signal data passing between the tag and monitoring devices tr> be sampled at prc-dctcrmined time intervals.

   t7. \ tag monitoring system according to claim 16 wherein the timing means is in the form of timing logic circuitry provided in the tag ancl/or monitoring devices.

   18.1\ tag monitoring system according to any preceding claim wherein the airborne signals arc in the form of radio wave signals. 19.A tag monitoring system according to any preceding claim wherein the threshold value of the strength detection means is set by a user of the system.

   20.;\ tag monitoring system according tc' any preceding claim wherein the threshold value of the strength detection means is set by the manufacturer of the system.

   21. A tag monitoring system according to any preceding claim wherein the alarm means includes any or any combination calf an audio, visual or kinaesthctic alarm.

   22. A tag monitoring system according to any preceding claim wherein the tag device and/or monitoring device arc providc1 with on/off switches to move the devices between operational and non-operati'nal conditions.

   23. A tag monitoring system according to any preceding claim wherein the tag and/or monitoring device is secured to an article or person via any or any combination of adhesive, clips, nut and bolt, VlL( llO, integrally f<rmcd with an article, as part of a smart card, SIM card or mcm'ry card, stitchcl ins' fabric of an article or clothing, via a keyring and/or kept in the pocket of clothing or compartment of an article.

   24. tag monitoring system according to any preceding claim wherein a tamper proof sensor is provided on the tag device and/or monitoring dcvicc, such that if an attempt is made to physically remove the device from an article to

   which it is attached, a warning signal or alarm is generated in sync or both of the devices.

   25.,\ tag monitoring system according to any preceding claim wherein the tag device is located on an article of value and the monitoring device is located with a user.

   26.A tag monitoring system according to claim 1 wherein the signal strength detection means includes receiving means, detection means, an operational amplifier data slicer and dynamic logarithmic detector.

   27.1\ tag monitoring system according to claim 2 wherein the at least two idcutical signals are transmitted substantially simultaneously on two different channels.

   28. A tag monitoring system according to claim 2 wherein the at least two identical signals are transmitted sequentially on a single channel.

   29. tag device for use with a tag monitoring system according to claim 1.

   30. A monitoring device for use with a tag monitoring system according to claim 1.

   31. \ tag monitoring system including a monitoring device and a tag device, each of which is provided with signal receiving and transmitting means, said monitoring device and said tag device being capable of remotely communicating with each other over a pre-determined range using airborne signals transmitted and received by said signal receiving and transmitting means, and wherein the tag device communicates with the monitoring device by

   transmitting at least two signals representative of substantially identical information and being spaced from one another in time and/or frequency, said monitoring device being provided with circuitry capable of detecting said at least two signals and decoding the same to identify when said tag device is within a prc-determincd distance of the monitoring device.