GB2276025A - Radio tag alarm system - Google Patents

Abstract

The alarm system includes a transmitter 21 which can be carried by a child and a receiver 10 carried by the child supervisor, the receiver giving an alarm signal if the child is beyond the transmitted signal distance. The transmitter is adapted to provide a signal, the receiver including electrical circuit components arranged so that the receiver is disabled by the signal from the transmitter but adapted to energise alarm means when not so disabled, there being personal retention means for the transmitter, the transmitter and receiver being independently portable whereby to permit monitoring of the position of a person retaining the transmitter relative to a movable location or base for the receiver. The personal retaining means is in the form of a releasably two-part coupling 21- 23, the transmitter being energised only when the two parts are coupled. <IMAGE>

Description

RADIO TAG ALARM SYSTEM FIELD OF THE INVENTION This invention relates to a radio tag alarm system, and in particular to a radio tag alarm system which includes a transmitter which can be carried by a child, perhaps concealed in the child's clothing, and a receiver carried by the child supervisor, typically a parent, the receiver giving an alarm signal if the child is beyond the transmitted signal distance.

BACKGROUND TO THE INVENTION The problem of a young child of walking age straying whilst the parent is temporarily distracted, perhaps during shopping, is well documented. Also well documented is the problem of a younger child, not yet able to walk, being left in a perambulator temporarily outside a (crowded) shop, and being unlawfully removed and abducted. These problems of "child-minding" are increased if the parent has more than one young child to supervise.

We have realised that an "early warning" system would increase the chance of a child being recovered, either before straying too far or before an abductor has escaped the vicinity.

DISCLOSURE OF THE PRIOR ART We are aware of British Patent application GB-A-2,248,331 to a surveillance alarm system, suitable for use when excursions of a body outside a predetermined zone take place.

We are also aware of British Patent 1,417,086 which discloses an electrical circuit which can be modified to function with a transmitting antenna located centrally within an area to keep an animal, the animal receiving an electrical shock if it moves outside the range of the transmitter. The unit is powered by miniature dry cell battery.

DISCLOSURE OF THE INVENTION Disadvantages of those radio tag alarm systems previously proposed and of which we are aware could include that the transmitter is difficult to disable when not required; frequent battery replacement or re-charging is necessary, which can be irritating and perhaps lead to the system being discarded as too troublesome; that the transmitter cannot easily be attached to and removed from the child's clothing, for instance for transfer to another clothing item if a change of clothing is desired; and that the unit has removable parts which if detached a baby can swallow.

We thus propose a radio tag alarm system including a transmitter and a receiver, the transmitter being adapted to provide a signal, the receiver including electrical circuit components arranged so that the receiver is disabled by the signal from the transmitter but adapted to energise alarm means when not so disabled, there being personal retention means for the transmitter, the transmitter and receiver being independently portable whereby to permit monitoring of the position of a person retaining the transmitter relative to a movable location or base for the receiver.

Usefully, the retention means includes a coupling having a first part and a second part, the first part being releasably connectable with the second part, the signal not being provided when the said first and second parts are not connected.

Preferably we select an audible alarm signal.

Desirably the transmitter and retention means are designed as a padlock, which when the second part is coupled at the second position forms a closed loop which can embrace part of the child's clothing, such as a name tag at an outergarment collar, or a zip fastener.

The second part can be coupled at the second position in one of a number of ways. In its simplest form the second part can be a press fit into part of the transmitter body housing the transmitter components. Alternatively the second part can have a bayonet fitting or a threaded end requiring the retention means to be flexible in order that it can be rotated during securement and retention. In a preferred arrangement, providing a secure coupling without need to rotate the retention means, we utilise a locking pin movably located in the transmitter housing and which can adopt an "inner" condition in which the second part can be locked in the transmitter housing and an "outer" condition in which the second part can be removed from the housing.

In this alternative arrangement, usefully the locking pin needs to be moved to the outer condition before the second part can be inserted in the housing, but in an alternative arrangement the locking pin and second part have complementary engagement surfaces whereby the locking pin is pressed back from its inner condition to its outer condition during insertion of the locking pin. The locking pin can have a bulbous end, of a size to be gripped between the fingers or less desirably to receive a removal implement, which if the bulbous end includes a lock could be a key.

Desirably the retention means includes a circuit element.

Thus if the retention means is severed or broken, leaving the second part in the second position, the transmitter is again disabled. Alternatively, the second part when in its second position provides a part of the circuit for the transmitter.

The receiver may incorporate timing means, so that the absence of the reception of a signal from the transmitter only in excess of a specified period of time causes the receiver to energise the alarm.

In a modified system the receiver includes circuitry adapted to respond separately to the disparate signals, whereby one receiver can monitor that more than one child has remained within range. For a different reason, the transmitter circuit preferably includes means to alter the transmitted signal, so that the system supplier can seek to avoid duplication of transmitted signal such as might occur if two similarly programmed transmitters were used within the transmission field, to give a false indication that a child was still within range.

Conveniently the signals from different transmitters are on one wavelength, the separate signals being distinguished by the imposed transmission pattern.

SHORT DESCRIPTION OF THE DRAWINGS The invention will be further described by way of example with reference to the accompanying drawings, in which Fig.1 is a schematic view of circuit elements in a receiver; Fig.2 is a side view of a transmitter; Fig.3 is a view corresponding to that of Fig.2 of an alternative embodiment of transmitter; Fig.4 is a schematic showing of the timing of multiple signals from one transmitter; and Fig.5 is a schematic showing of the timing of three alternative signals for a transmitter.

DESCRIPTION OF THE EXEMPLARY EMBODIMENTS The circuit components of receiver 10 are located in a suitable housing (not shown) which can be carried by a child supervisor or minder, typically a parent. Usefully the housing will be attached to a strap so that the receiver can be secured to an outer clothing item, or to the handle of a supermarket trolley or the like, but this is not essential. The receiver 10 in this embodiment is of a low power type powered by a miniature dry cell battery.

Checking means as known in the art can be provided both to confirm that the receiver is functional and that the battery retains sufficient operating power.

The circuit components process a signal received by aerial 11, connected to a resonant circuit 12 to form a tuned antenna presenting a high impedance to the selected signal frequency. Other frequencies are attenuated or rejected in known manner, as by being shunted to ground.

The processed signal from resonant circuit 12 is fed to a voltage amplifier 13, in this embodiment a Darlington pair of high gain. In known fashion the operating point of the amplifier can be set by bias resistors.

The alternating output from the voltage amplifier 13 is converted to a D.C. voltage by rectifier 14.

The rectified signal is fed in this embodiment to a combination low power amplifier and capacitor unit 15. The low power amplifier is provided for charging an energy storing capacitor, which when charged is used to power an oscillator circuit 16, in this embodiment an astable multivibrator.

The amplified signal is also used to hold a circuit component, usefully a transistor, in its cut-off region so preventing the capacitor becoming charged; if charged the capacitor will power an oscillator circuit 16; the oscillator circuit 16 of this embodiment produces a square wave output signal which is amplified by circuitry in audible warning unit 17 whereby to provide power to the coil of an audible sound emitter, so providing a warning indication. In an alternative embodiment an alternative warning is given, such as a warning light. In a further alternative embodiment, both an audible and visual warning is given.

If a signal is received by aerial 11 and processed, then oscillator circuit 16 is disabled. If no signal is received by oscillator circuit or if a signal fails to excite resonant circuit 12, the oscillator circuit is energised to cause audible warning unit 17 to emit a warning sound. In an alternative embodiment, a delay means may be included so that the transmitted signal must be absent for a period of time e.g. four seconds, before the warning signal is emitted; this embodiment would prevent an unwanted warning if the transmitted signal is temporarily blocked, for example, by a passer by coming between the child and the parent.

In further alternative embodiments of the invention, any circuit which is normally in the "on" state to provide a warning signal, but which is maintained in the-"off" state by the presence of a received signal, would be suitable as a receiver.

Transmitter 20 is carried by the child. It includes a housing 21 enclosing the transmitter circuitry (not shown) in known fashion and arrangement, and a strap 22 which includes the transmitter aerial. Thus if the strap 22 is disconnected as shown in Fig.2, or is connected as shown in Fig.3 but cut or otherwise severed, no signal is transmitted, and the parent's alarm 10 is activated.

In the embodiment of Fig.2 the first end 22a of strap 22 is firmly connected to housing 21 at a first position 21a.

Second end 22b of strap 22 has a first coupling part 23 adapted for insertion into housing 21 at second position 21b.

In the embodiment of Fig.2, the first coupling part 23 is a press fit into a second coupling part located in a housing recess at second position 21b. In an alternative embodiment the first and second coupling parts provide a bayonet type connection, whilst in yet a further embodiment the first coupling part is externally threaded and the second coupling part internally threaded for a screwed connection.

In the embodiment of Fig.3 the first coupling part 23 has a lateral recess adapted to receive pin 30. Only if pin 30 is moved from its "inner" position as shown (where it holds coupling part 23 against removal, vertically as viewed in Figs 2,3) can the first coupling part be removed from electrical contact with the second coupling part to break the transmitter circuit. The pin 30 has a bulbous end 31 by which the pin can be grasped by the fingers to withdraw the pin from the housing 21 as far as permitted i.e. to its "outer" position, still however retained by the housing against complete removal. In a less preferred embodiment the bulbous end can locate a lock body such that the pin can only be moved from its inner to its outer position after release of the lock by a key.

In an alternative embodiment, the pin 30 may req uire to be pressed towards the housing to release the first coupling part.

In another embodiment, the end of the first coupling part is electrically conducting, and when inserted into the housing at position 21b engages two electrical terminals to complete the electrical circuit to operate the transmitter.

In this embodiment, no current is required to flow around the strap, so that it may suitably be of a strong but flexible plastics material. Location of the first coupling part in the housing could be by press fit as in the Fig.2 embodiment, or by a pin engagement as in the Fig.3 embodiment.

The strap 22 and housing 21 are shaped to padlock form, with the strap adapted for quick securement to a child's outer garment. Release of the strap to the Fig.2 condition when the transmitter is not in use will prolong battery life.

In a preferred embodiment, the transmitter will emit only one signal, repeated at specified intervals. One cycle for a signal 40 is shown in Fig.4, comprising a first pulse 40a and a second pulse 40b at a specified time thereafter.

The receiver 10 is programmed to respond to the signal 40, to disable warning indicator 17, which is therefore silent whilst transmitter 20 is emitting within range of the receiver.

In a first modified arrangement permitting the system to be readily re-programmed to avoid false indications from another (third party) system the transmitter can emit a selected one of a number of different coded signals, usefully at the same frequency. Thus the transmitter may be easily re-programmable from signal 40 to signal 41 or signal 42 (Fig.5). In this embodiment the different signals are emitted as different patterns of pulses, signal 40 being of two pulses at the "0" and "5" time intervals; signal 41 being of three pulses at the "0", "4" and "5" time intervals; and signal "3" being at the "0" "3","4","5" time positions.Thus if the user of the system discovers that a third party has a transmitter emitting an identical signal, then his system may be readily reprogrammed to an alternative, non-identical signal.

For monitoring the presence of several e.g. three children within a specified range, one receiver can respond to each of three different signals. Thus different signals of a common cycle time can be emitted by three tranmitters, one for each child. In this case the signals must not conflict i.e. to avoid receiver confusion, the signals from the three transmitters must be selected to be without overlap e.g. at positions "0,1"; "0,3" and "0,5". In a more advanced arrangement the three signals are processed sequentially. Only if each of the separate signals is received at some time during a selected number of cycles is unit 17 rendered inoperative.

The pulse length is conveniently 1 millisecond, with a total cycle time of 20 milliseconds.

In yet a further embodiment, the unit 17 can be programmed to give an increasing warning e.g. a louder sound, as the transmitter moves towards its out of range condition. Thus the amplified signal as above described, used to hold the transistor at cut-off, would gradually diminish; the capacitor would be charged more or less quickly to power the oscillator circuit.

It will be understood that the operating range within which the transmitter must be in relation to the receiver can be set according to the strength of the transmitted signal and the amplification of the receiver. In one embodiment of the invention, the amplification of the receiver may be variable according to the wishes of the child's supervisor, so that the child may move some distance from the parent in a relatively unpopulated area such as a park or garden before a warning is given, but have a more limited range in a busy shopping area.

The invention will also be of use if the tranmitted signal is blocked or screened for an extended period of time, for example if the child strays into a neighbouring aisleway of a shop, since such straying may later lead to the child being abducted.

In another embodiment of the invention, the first and second coupling parts are attached to respective first and second flexible straps, which straps are each attached to the transmitter housing. In this embodiment, it is not necessary to provide a coupling part within the housing, the housing only requiring means to attach the two straps.

The coupling parts may be of any suitable form, but are usefully in the form of a jewellery clasp, so that they may be readily uncoupled by a parent, but not readily uncoupled by a child or infant lacking the manual dexterity required.

In such an embodiment, the first and second straps are desirably of different lengths, so that if the transmitter hangs from e.g. a zip fastener, the coupling parts are not in contact with the zip fastener.

Claims (15)

1. A radio tag alarm system including a transmitter and a receiver, the transmitter being adapted to provide a signal, the receiver including electrical circuit components arranged so that the receiver is disabled by the signal from the transmitter but ' adapted to energise alarm means when not so disabled, there being personal retention means for the transmitter, the transmitter and receiver being independently portable whereby to permit monitoring of the position of a person retaining the transmitter relative to a movable location or base for the receiver.

2. A radio tag alarm system including a transmitter and a receiver, the transmitter being adapted to provide a signal, the receiver including electrical circuit components arranged so that the receiver is disabled by the signal from the transmitter but adapted to energise alarm means when not so disabled, personal retention means for the transmitter, the retention means including a coupling having a first part and a second part, the first part being releasably connectable with the second part, the signal not being provided when the said first and second parts are not connected, the transmitter and receiver being independently portable whereby to permit monitoring of the position of a person retaining the transmitter relative to a movable location or base for the receiver.

3. A system according to claim 2 in which the retention means includes strap means formable into a closed loop, the signal also not being provided if the strap means are severed.

4. A system according to claim 2 or claim 3 in which said alarm means is one of an audible alarm, a visual alarm, and an audible and visual alarm.

5. A system according to any of claims 2-4 in which the first part of the coupling is attached to one end of a flexible member, the opposed end of the flexible member being attached to the transmitter, and in which the second part of the coupling is integral with the transmitter.

6. A system according to any of claims 2-5 in which the first part of the coupling is attached to one end of a first flexible member, and in which the second part of the coupling is attached to one end of a second flexible member, the opposed ends of the said first and second flexible members being attached to the transmitter.

7. A system according to claim 6 in which the said first and second flexible members are of different lengths.

8. A system according to any of claims 2-7 in which the receiver incorporates timing means for providing a delay between termination of reception of'the signal and energising of the alarm means.

9. A system according to any of claims 2-8 including one receiver and a plurality of transmitters, the signal from each of the said transmitters being a series of pulses, the timing and duration of the pulses being different for each of the said transmitters.

10. A system according to any of claims 2-9 in which the receiver includes amplification means, and in which the said amplification means is adjustable by the operator.

11. A transmitter for use with a system according to any of claims 1-10.

12. A receiver for use with a system according to any of claims 1-10.

13. A transmitter constructed and arranged substantially as described with reference to Fig.2 or Fig.3 of the accompanying drawings.

14. A receiver constructed and arranged substantially as described with reference to Fig.1 of the accompanying drawings.

15. A radio tag alarm system constructed and arranged substantially as described with reference to any of Figs.l-5 of the accompanying drawings.