GB2224146A - Intruder alarm system - Google Patents

Abstract

The system is of the type comprising a warning device 14 and an intruder detection device 22, 24, the warning device being remote from the intruder detection device, wherein the warning device and the detection device are connected by an infra-red link 18, 30. The latter preferably includes an arrangement for sending coded, infra-red pulses to a receiver which, while receiving correctly coded pulses, maintains the warning device de-activated. Upon detection of intrusion, the transmission of the infra-red pulses is halted whereby the receiver causes the warning device to be activated. The detection device is preferably provided in a vehicle, in which case the receiver and warning device are located in a house or other premises so as to enable reception of the transmitted infra-red pulses. <IMAGE>

Description

INTRUDER ALARM This invention relates to an intruder alarm, and in particular to an intruder alarm of the type comprising a warning device and an intruder detection device, the warning device being remote from the intruder detection device, this particular type hereinafter being referred to as an intruder alarm of the type described.

Intruder alarms of the type described have been known for many years, for instance to alert the owner or his representative of unauthorised intruders in buildings; for such applications the warning device is often an audible warning device positioned on an outside wall and connected by cable to one or more intruder detection devices within the building. However, an intruder alarm which relies on a cable connection has only a limited range of uses. Thus, whilst intruder alarms using a cable to connect the intruder detection device to the warning device can be adapted for fitting to a garage, to warn of intruders who seek to break into the garage to steal, or steal from, a garaged car, they are not suited to fitting in or on the car itself, primarily because the cable cannot be left permanently fitted to a car which is in daily use.Furthermore, if the car user does not have an available, lockable garage for the car so that the car is parked for instance in the home driveway or under a car port, the car driver is likely park his car on different occasions at slightly different positions, perhaps beyond the reach of the cable. If the car is parked in the road outside his home, or-in a car park at his place of work, the problem of connecting a cable is even greater. If the driver is visiting friends, or travelling and staying overnight at a motel or hotel, they are unlikely to have a suitable cable or be willing to fit one.

One known vehicle intruder alarm of the type described, and intended for use on or in vehicles, has a warning device in the form of a bleeper carried by the car driver and activated by a radio signal from the intruder detection device. However the car needs a radio aerial; the radio aerial transmits through 360 degrees and therefore consumes significant power; the car driver may unwittingly move into an area shielded from the radio signal; many countries allocate and license permitted radio frequencies, and an intruder alarm suitable for use in one country may be unlawful in another.

In-car alarms are known, but these may not be heard if the car driver is inside his home, especially if the car is parked some distance away, such as at the end of a garden; or may be ignored if the alarm issues an audible warning similar to those of other car alarms.

We now propose an intruder alarm of the type described, and which avoids or reduces the above problems.

Thus we propose an intruder alarm of the type described, in which the intruder alarm includes an infra-red link between the intruder detection device and the warning device. Preferably the infra-red link is directional, conveniently being transmitted in a cone of included angle of less than 90 degrees, desirably less than 10 degrees.

Although infra-red radiation has been used for some years as a communications link, both channelled as in a fibre optic cable for pulsed signal transmission, and unchannelled as when used to operate remote switches e.g. for remote TV control, its usefullness as a directional link in a vehicle intruder alarm system has not to our knowledge previously been appreciated.

Preferably the intruder detection device also includes an emitter for ultrasonic radiation and a detector responsive to changes in the reflected pattern of said ultrasonic radiation, whereby to sense movement e.g. within the car in which the intruder detection device is positioned; the warning device will then produce a warning signal when the infra-red radiation is interrupted, either directly by an intruder passing between the warning device and the intruder detection device, or indirectly by an intruder moving within the ultasonic pattern.

The warning device will normally be energised from the mains electrical supply, but alternatively from a battery. When so energised it will have a first activated condition and a second de-activated condition, the warning device normally being held in the de-activated or non-warning condition by the infra-red electromagnetic beam. Preferably, when energised but in the de-activated condition, an indicator light on the warning device will be illuminated. Usefully the warning device is portable or semi-portable.

The intruder detection device will normally be powered by a battery, conveniently for a car alarm by the car battery by way of the cigar lighter, and will also be portable.

The intruder detection device will be behind a car window e.g the windscreen. The warning device will usefully be positioned within a dwelling occupied for instance by the car driver, but situated behind a window or other transparent but rigid barrier.

Thus someone wishing to intrude into the car without immediate detection cannot do so without the deterrent complication of first needing to break into the dwelling in order to disable the warning device.

The invention will be further described by way of example with reference to the accompanying drawings in which: Fig.1 is a schematic arrangement of an intruder alarm according to the invention; Fig.2 is a schematic block diagram of the functional components of an intruder alarm, generally according to Fig.1 but with an integral ultrasonic emitter/detector; and Fig.3 is an example of a coded pulsed "link beam", for use in the invention.

The intruder alarm 10 comprises an intruder detection device 12 and a warning device 14.

The intruder detection device 12 is energised by way of coupling 16 fittable into the cigar lighter on the vehicle dashboard (not shown), and when so energised it transmits radiation in the infra-red frequency range in the direction a and with a spread angle b, by way of transmitter device 18; in this embodiment the conical spread angle b is 10 degrees; but in an alternative embodiment is up to 90 degrees. Coupled to the intruder detection device is an ultrasonic unit 20 having emitter 22 and detector 24, though in an alternative embodiment more than one emitter/detector is used, and these are combined into a single body. In a further alternative embodiment (also as seen in Fig.2) the ultrasonic unit 20 is integral with the intruder detection device 12.The ultrasonic unit 20 is programmed so that any change in the pattern of reflected ultrasonic radiation sensed by detector(s) 24 causes an interruption in the radiation transmitted by the intruder detection device 12 i.e. by transmitter device 18.

The warning device 14 includes a receiving device 30 responsive to infra-red radiation. Thus when the warning device 14 is coupled by plug 32 to the mains electricity supply and so is energised, correctly programmed signals reaching receiving device 30 disable sounder 34; but interruption of the infra-red signal pattern to which receiving device 30 is programmed causes sounder 34 to issue an audible alarm. In an alternative embodiment, sounder 34 is replaced by a visual warner, or other warner.

Sounder 34 may also be connected to energise an existing intruder e.g. burglar, alarm.

In use, the intruder detection device 12 is positioned inside a car, behind the windscreen or door window or rear window, and the warning device 14 is positioned behind a house window (or in an alternative embodiment behind an apertured grill). With both devices energised, they are aligned so that the beam transmitted in direction a impinges upon the receiving device 30. The intruder detection device 12 is then switched to the fully-on or operative condition in which the ultrasonic unit 20 is operative to emit ultrasonic radiation. The warning device 14 is then switched to the fully operational condition; in an alternative embodiment the warning device is switched to the fully operational condition before the intruder detection device.

Both devices have an inbuilt time delay in order that the person setting the intruder alarm will not trigger it. Thus the warning device has two modes of operation, the first mode being used whilst the transmitter is being lined up into the line of sight, when no warning sound is emitted, and the second mode being the alarm mode; in this embodiment the transfer from the first to the second mode occurs automatically after a pre-set delay, which can be varied. The in-vehicle unit 12 also has an inbuilt delay to permit the vehicle doors to be locked, after the intruder device 12 has been energised, without the transmitting device 18 transmitting a warning signal. Sounder 34 has a timed alarm period, which period can be varied; and there are also means to re-set the sounder 34 to the non-sounding condition by way of a re-set button 146 (Fig.2).

So long as the infra-red transmitting device 18 in the protected vehicle beams a signal in the optical line of sight (direction a) to the receiving device 30 in the window of the dwelling, the warning device 14 is held in its non-warning condition. If however the pre-set infra-red beam pattern is interrupted, directly as by an intruder passing between the transmitter 18 and the receiving device 30, or indirectly as by a motion sensor in the vehicle being tripped, or the intruder detection device 12 in the vehicle being unplugged, then the sounder 34 is set off.

In this embodiment, both the intruder detection device 12 and the warning device 14 are portable; and as will be appreciated they are not connected except by the transmitted infra-red beam.

No additional wiring is required in the vehicle i.e. additional to that provided by the vehicle maker.

In the arrangement of Fig.2, a pulse generator 121 is provided to pulse the transmitting device 18 output, to provide a short burst of signal-time X and a long off-time Y (Fig.3). Thus a high transmitter signal output can be achieved, allowing a greater range for the signal, but with low average power consumption.

The signal can thus have a range of over 100 meters, perhaps up to 200 meters; this longer range signal could be useful for cars parked outside high flats or tall office buildings, and then usually the warning device will be fitted with a high intensity alignment indicator lamp, or in an alternative embodiment with its own transmitting device e.g. infra-red, to alert the operator setting the warning device when the devices are in alignment. A conveniently pulsed modulated beam will transmit with 300 micro seconds on, and 100 milliseconds off, with the receiver circuitry integrating over a period of time. Preferably the bursts of signal-time will not exceed 50 milliseconds, with a space to burst time ratio up to 1000 to 1, but not less than 10 to 1.The actual frequency of bursts of signal should allow the infra red link to be continuously broken for two seconds before the warning device is triggered (so that passing animals or persons will not raise a false alarm), and for reliable monitoring a plurality of bursts should have been transmitted during this two second period.

Code generator 122, which in this embodiment is set up by the user, conveniently with on-off switches, determines the code to be impressed on the signal, from a number of available codes.

The selected code will be chosen to avoid interference from the signals of other local intruder alarms of the same type, and also to limit the possibility of tampering by unauthorised third parties with the in-vehicle transmitter unit. One signal code is shown in Fig.3.

A transmitter inhibit 123 will turn off the transmitter signal when an input is received from the ultrasonic unit 20. Operation of the transmitter inhibit acts to set off the alarm in the in-house receiver unit 14, by way of the directional infra-red coded beam, as above described.

The ultrasonic motion and/or intruder detection unit 20 comprises an ultrasonic sound emitter 22 and an ultrasonic sound receiver 24. The emitter 22 sets up a sound pattern in the vehicle, whilst the receiver detects any change in the received pattern, the unit 20 sending a signal to the transmitter inhibit 123 if there is such a change.

In the Fig.2 embodiment, the ultrasonic unit 20 is inhibited from commencing operation for 30 seconds from initial energisation, in order to allow the car user to align the in-vehicle device 12 with the in-house device 14 i.e. to set the infra-red link. However, in order that an unauthorised intruder will not be able to "permanently" inhibit the ultrasonic unit, by repeated plugging and unplugging of the connection 16 within this 30 second time period, the circuitry of the ultrasonic unit 20 permits unit 20 to remain powered (by way of an internal electrical storage device) for a period of 5 seconds; this is to allow the transmitting device to "power down" before the ultrasonic unit i.e. with loss of the infra-red link before the 30 seconds have elapsed in which the ultrasonic "power on" inhibit can be re-set.In an alternative embodiment, the time periods of 30 seconds and 5 seconds are different selected time periods; and in yet a further alternative embodiment these time periods can be changed by the equipment supplier, and possibly by the car user.

Connected to the transmitter inhibit 123 is an auxiliary input 124; by connecting the auxiliary input 124 to other security intruder alarms (some of which may be connected by cable), the in-vehicle unit 14 can have a wider application.

An infra-red light emitting diode driver 125 gives a high powered drive to the infra-red light emitting diode 126 forming transmitter 18. The diode 126 emits a signal in accordance with the instruction from the pulse and code generators 121, 122.

Preferably, the coded pulses are in the form of bursts having a short burst-time X and a long off-time Y as seen in Fig.3.

As indicated in Fig.2, the in-house receiver alarm or warning device unit 14 also has a number of functional blocks.

An infra-red receiver-amplifier 141 amplifies the infra-red signal received from the infra-red receiving device 30.

A decode unit 142 compares the incoming signal code with a preset code lodged in the in-house unit 14. In one embodiment the pre-set code is fixed; whilst in a further embodiment the pre-set code can be altered to one of a number of pre-set codes, or can be further changed by the equipment supplier and possibly by the car owner. In this embodiment, if the incoming code is identical with the pre-set code, signal aquisition lamp 143 is illuminated, as well as the signal being passed on to the timer 144; if the codes do not match, then the lamp is not illuminated and the signal is not passed through to the timer.

Timer 144 is activated by the loss of a currently-coded pulse; and is re-set during the timing period allowed before the reception of a further correctly-coded pulse. If however a correct currently-coded pulse is not received within the time allowed (conveniently 2 seconds or less), the timer initiates a signal to the alarm control 145.

The alarm control 145 has three modes of operation {a} mode 1 wherein switch 146 is in the off position and the receiver is not energised i.e. it is powered down; {b} mode 2 in which switch 146 is in the "set" position, in which no audible alarm is sounded even though there is loss of signal, so that there is merely a visual indication at lamp 143; and ic) mode 3 in which switch 146 is in the "alarm" position, wherein there can be an audible and visual indication of loss of signal, in one embodiment continuing for a preset time period. The in-house unit 14 may be re-set out of mode 3 by switch 146 during the timed period in order to mute the alarm. Once the timer has timed out or been re-set, it is re-triggered only by loss of signal.

In an alternative embodiment, the in-house unit 14 can respond to the infra-red signals from more than one transmitting device 18. Thus in one embodiment, four in-vehicle devices 12, one in each of four cars on a driveway, are aligned with a single in-house device 14, the in-house device 14 initiating the warning alarm if any one of the in-vehicle devices 12 "senses" an intruder (by monitoring a change in the reflected ultrasonic pattern), or if any of the directional links provided by the infra-red beams between devices 12 and 14 are broken, and the break persists for more than the pre-set period.

In use, the in-house unit will be positioned inside the dwelling, conveniently on a window sill, to give an unobstructed view of the vehicle to be protected. Plug 32 is then connected to the power supply, which is switched on. The control switch 146 on warning device 14 is then moved to the "set" position.

The car owner or user then returns to the vehicle, to plug in connector 16 to the cigar lighter. The in-vehicle device 12 is then positioned e.g. on the dash hoard or clipped to the sun visor or steering wheel, so that transmitting device 18 is aligned with receiving device 30. With the in-vehicle unit powered and the transmitting device 18 and receiving device 30 in proper alignment, indicator light or aquisition lamp 143 is illuminated, with sufficient intensity to be seen from within the car.

The ultrasonic unit 20 is also positioned in the car, conveniently on the dash board, and is plugged into the inhibitor component 123; though in an alternative embodiment (Fig. 2) the ultrasonic unit 20 is made integral with the in-vehicle unit 12.

With the indicator light 143 illuminated, the vehicle doors are closed and locked.

The car owner returns to the house, to set the control switch 146 on the in-house device to the "alarm" position, so that the alarm is set i.e. the intruder alarm is operative to help protect the vehicle.

An advantage of using infra-red radiation for the signal link between the intruder detection device and the warning device is that the signal is invisible. Another advantage is that it is only slightly absorbed in water and so has a greater range in normal atmospheric conditions than light (in the visible spectrum) and this gives additional security in hazy or misty conditions when vehicle intruders are likely to be active. A third advantage is that it can be made directional, to operate over a narrow angle, and that it can be pulsed so that it involves low drain from the vehicle battery. A fourth advantage is that the signal can be coded.

Although primarily intended for protecting a vehicle left outside the dwelling e.g. on the drive or in a car port, the intruder alarm can also be used to help protect buildings, such as garden sheds or outhouses, caravans, detached garages and the like. In particular, whilst in the above embodiments the receiving device 30 is in the direct line of sight of transmitting device 18, in alternative embodiments the infra-red beam can be reflected towards the warning device; or the infra-red transmitter can be mounted on an exterior wall and itself activated by a signal from a warning device to which it is connected by cable.

If desired,a number of warning devices can be assembled behind for example an office window, each responsive to its respective intruder detection device positioned in a staff car parked outside the office.

Claims (12)

1. An intruder alarm of the type described, which includes an infra-red link between an intruder detection device and a warning device.

2. An intruder alarm as claimed in claim 1 in which the infra-red link is directional, with a limited angle of spread.

3. An intruder alarm as claimed in claim 2 in which the infra-red link is transmitted in a cone having an included angle of less than 90 degrees.

4. An intruder alarm as claimed in claim 3 in which the included angle is less than 10 degrees.

5. An intruder alarm as claimed in any of claims 1-4 in which the intruder detection device is located in a vehicle, and the warning device is located in a dwelling, the intruder alarm being a vehicle intruder alarm.

6. An intruder alarm as claimed in claim 5 in which the vehicle is a car, and the intruder detection device is located behind the car windscreen.

7. An intruder alarm as claimed in any previous claim in which the intruder detection device includes an emitter for ultrasonic sound and a detector responsive to changes in the reflected pattern of said ultrasonic sound, the detector being adapted to respond to intruder movement within the vehicle to effect interruption of said infra-red link, and thus operation of said warning device.

8. An intruder alarm as claimed in any previous claim in which the warning device is energised by a mains electrical supply, and in which the warning device is adapted when so energised to switch between a first activated condition and a second de-activated or non-warning condition, the warning device being adapted to be held in the de-activated condition by the presence of the infra-red link and to revert to the activated condition when said infra-red link is interrupted.

9. An intruder alarm as claimed in claim 8 in which the warning device includes an indicator light adapted to indicate that the warning device is energised.

10. An intruder alarm as claimed in any of claims 7-9 in which the intruder detection device is powered by a battery.

11. An intruder alarm as claimed in any previous claim in which the infra-red link comprises a series of coded pulses.

12. An intruder alarm constructed and arranged substantially as described in relation to the accompanying drawings.