GB2599903A

GB2599903A - A security system and associated methods

Info

Publication number: GB2599903A
Application number: GB2016179.0A
Authority: GB
Inventors: Laporta Giovanni
Original assignee: Individual
Current assignee: Individual
Priority date: 2020-10-12
Filing date: 2020-10-12
Publication date: 2022-04-20
Also published as: GB202016179D0

Abstract

A security system 100 comprises a first sensor 110 and a magnet 120. The first sensor 110 is mounted to a frame 14 of an openable door or window, whilst the magnet 120 is mounted to a leaf 12. The first sensor 110 may be three axis magnetometer that detects position of the corresponding magnet 120 in three co-ordinate axes. The security system 100 is calibrated in-situ during initial setup. The leaf is placed in a number of positions (such as closed, marginally closed and open). In each position, the magnetometer output is registered and a corresponding location point in a co-ordinate system identified. For each location point, a bounding space 210,211,213 is then defined, each location point being within a bounding space. The bounding space may be a predefined tolerance for each respective position. In another aspect, a system may determine whether a sensed location point falls outside of a predetermined bounding space and generate an alert accordingly. In a further aspect, a second sensor may be provided wherein each sensor may have a normal and activated state dependent upon an applied magnetic field. In another aspect, a first sensor detects whether a leaf has been moved or knocked.

Description

A security system and associated methods

Field of the Invention

The present invention relates to security systems for windows and doors. The invention also relates to methods for calibrating and methods employing such systems or devices.

Background to the Invention

Detection systems that detect whether a door/window has been opened are available. The vast majority of these known detection systems employ reed switch assemblies, each comprising a magnet and a reed switch. The magnet is installed onto the leaf and the reed switch onto the frame, or vice versa. The reed switch is activated when the magnet is proximate to the reed switch (i.e. when the door/window is closed). A disadvantage with such systems is that they are very easy to defeat by intruders. An intruder can tamper with a reed switch assembly simply by placing any off the shelf generic magnet close to the reed switch. This gives the monitoring system a false reading to report that the window or door is closed and secure. Therefore an intruder wishing to break into a building can place or affix a generic magnet close to the reed switch to signal to the monitoring system that the window/door is closed. The leaf can then be opened without the reed switch detecting that the magnet on the leaf has moved away from the reed switch.

Summary of the Invention

According to a first aspect of the invention there is provided a method of calibrating a security system for a window or door assembly, the security system comprising a first magnetic field generator and a first sensor for sensing a magnetic field, one of the first magnetic field generator and first sensor being mounted to a moveable element of the window or door assembly, the other being mounted to a reference structure that the moveable element is moveable relative to, the method comprising: receiving an output signal from the sensor when the moveable element is in a first position, using said output signal to derive a location point in a reference coordinate system corresponding to said position of said moveable element, and defining at least a first bounding space in the reference coordinate system, said location point being within the bounding space.

The security system may be used to monitor the position of the moveable element of the window or door assembly. The method of calibrating the security system is preferably an in-situ method of calibrating the security system. In other words, during calibration the moveable element is moved and the corresponding output signals of the sensor are recorded after the window or door assembly has been installed in a building at a particular geographical location. This contrasts from security systems which are set up ready for use during fabrication in a factory and prior to installation in a building.

The bounding space defines a predefined error tolerance for the security system. Whilst expensive magnetometers would allow very accurate determination of relative position of the corresponding magnet, by defining a bounding space in a reference coordinate system, lower cost sensors may be employed. The defined bounding space will suitably take account of noise, such as digital noise, environmental temperature etc which could affect the output signal from the sensor.

The output signals from the sensor suitably comprise digital signals associated with a measured magnetic field.

The method may comprise positioning the moveable element and receiving an output signal from the sensor at each of at least a first and second position of the moveable element, using said output signals to derive a location point in a reference coordinate system corresponding to each said position of the moveable element, and defining at least a first bounding space in the reference coordinate system, said location point being within said bounding space.

The method may comprise positioning the moveable element and receiving an output signal from the sensor at each of a plurality of positions of the moveable element, using said output signals to derive a location point in a reference coordinate system corresponding to each said position of the moveable element, and defining at least a first bounding space in the reference coordinate system, said location point being within said bounding space.

By reference to location points being with in the bounding space, this may include one or more location points being on the boundary of the bounding space.

Preferably the method is carried out in-situ. The method of calibrating the security system is carried out onsite, at the location where the window or door assembly has been installed.

Preferably an output signal from the sensor is received when the moveable element is in each of a plurality of positions and a location point in a reference coordinate system is derived from the output signal corresponding to each said position. The security system may be calibrated by moving the moveable element between at least two, or a series of, discrete positions and registering the output signal from the sensor for each position. Alternatively the method may be configured to continuously record output signals from the sensor as the moveable element moves along a continuous path between a start position and a finish position. In the latter embodiment, the method may be configured to continuously record output signals from the sensor as the moveable element moves along more than one continuous path.

Calibration parameters are established using the registered output signals from the sensor which correlate the measured magnetic field output from the sensor with location points in the coordinate reference system. Following calibration of the security system, when the security system is in a monitoring mode in which the position of the moveable element can be determined, the calibration parameters are applied to the output signals from the sensor to determine the position of the moveable element.

The method may include a step of using at least one characteristic relating to the window or door assembly as an input in determining the calibration parameters. The method may include a step of a user inputting data regarding at least one characteristic relating to the window or door assembly as an input in determining the calibration parameters. Said at least one characteristic may be the type of window or door assembly (e.g. casement window, tilt and turn window) and/or a dimension of the leaf. For a casement window, the dimension of the leaf from the hinged edge to the edge that engages the jamb may be input into the system for example. Input of such a dimension assists in extrapolating expected output values of the sensor when the leaf is at or near a fully open position, even if the leaf was not registered at such an extent of opening during the calibration process. This means that the same system can more easily be used with different sizes of leaf.

Preferably the step of defining at least a first bounding space in the reference coordinate system comprises defining a bounding form around each location point in the reference coordinate system that has been derived from an output signal of the sensor, each location point falling within its corresponding bounding form.

The bounding form is preferably a 3D shape (i.e. a bounding shape), but may alternatively be a 2D shape, such as a planar square, ellipse or circle, or a 1D line. Preferably the calibration method involves defining a series of overlapping bounding forms that define a single bounding space.

Preferably each bounding form comprises a cuboid shape. The bounding form may alternatively be any other 3D shape, such as an ellipsoid. Preferably the bounding form comprises a cube.

Preferably the method further comprises the step of recalibrating the security system to take account of changes in the Earth's magnetic field.

In preferred embodiments the location points in the reference coordinate system are adjusted to modified location points based on expected changes in the corresponding magnetometer output signals due to changes in the Earth's magnetic field. For example, modified location points may be derived by adding or subtracting new magnetic drift data from the output signals used to calculate the previous location points. In preferred embodiments adjusted bounding spaces are defined in the reference coordinate system based on the adjusted location points.

The security system may be configured such that recalibration takes place automatically (i.e. the security system self-recalibrates). The security system may be configured such that recalibration takes place periodically at regular predetermined intervals. For example, the security system may be configured to recalibrate once every year. The security system may also / alternatively be configured to recalibrate if the polar drift has exceeded a predetermined threshold since calibration or recalibration last took place.

According to a further aspect of the invention there is provided a program for carrying out a method according to any aspect of the invention as described above.

According to a further aspect of the invention there is provided a computer-readable medium storing a program according to any aspect of the invention.

According to a further aspect of the invention there is provided a security system for a window or door assembly, the security system comprising a first magnetic field generator and a first sensor for sensing a magnetic field, one of the first magnetic field generator and first sensor being mounted to a moveable element of the window or door assembly, the other being mounted to a reference structure that the moveable element is moveable relative to, the system further comprising a processing device configured to execute instructions to: receive an output signal from the sensor when the moveable element is in a first position, use said output signal to derive a location point in a reference coordinate system corresponding to said position of said moveable element, and define at least a first bounding space in the reference coordinate system, said location point being within the bounding space.

The processing device may be a server, a computer, or a mobile communication device for example. The processing device may alternatively comprise electronic circuitry configured to execute the relevant instructions. The processing device preferably has a memory for storing instructions relating to operation of the security system.

The processing device may be configured to execute instructions to allow the security system to be calibrated according to any aspect of the method of calibrating a security system as described above.

According to a further aspect of the invention there is provided a security system for a window or door assembly, the security system comprising a first magnetic field generator and a first sensor for sensing a magnetic field, one of the first magnetic field generator and first sensor being mounted to a moveable element of the window or door assembly, the other being mounted to a reference structure that the moveable element is moveable relative to, the system further comprising a processing device configured to execute instructions to: receive an output signal from the sensor when the moveable element is in a first position, use said output signal to derive a location point in a reference coordinate system corresponding to said position of said moveable element, and define at least a first bounding space in the reference coordinate system, said location point being within the bounding space, the system being adapted for calibration using a method according to any aspect of the invention described above.

The system is preferably configured to allow a user to input data relating to at least one characteristic of the window or door assembly. Said data may relate for example to the type of door or window assembly and/or a dimension of the door or window assembly. The system may include a user interface for inputting at least one dimension of the leaf or it may include a programming port for receiving an input relating to a dimension of the leaf.

The user interface may include a data input interface. The data input interface may be a key pad or touch screen or other suitable interface. Said data relating to at least one characteristic of the window or door assembly may be input by means of inputting a reference code to the system via a user interface, said reference code corresponding to parameters relating to window or door assembly characteristic stored in the system.

According to a further aspect of the invention there is provided a method of detecting if an extrinsic magnetic field generator has entered the proximity of a security system for a window or door assembly, the security system comprising a first magnetic field generator and a first sensor for sensing a magnetic field, one of the first magnetic field generator and first sensor being mounted to a moveable element of the window or door assembly, the other being mounted to a reference structure that the moveable element is moveable relative to, the method comprising: receiving an output signal from the sensor, the signal being associated with a measured magnetic field, deriving a sensed location point corresponding to the output signal in a reference coordinate system, determining whether the sensed location point falls within a predetermined bounding space defined in the reference coordinate system, the predetermined bounding space having been derived based on at least one output signal obtained from the sensor during a prior calibration process; and generating an alert signal if the sensed location point falls outside the predefined bounding space.

The method is intended to detect if an extrinsic magnetic field generator, such as an unauthorised magnet, is brought into the vicinity of the sensor.

The calibration parameters established during the calibration process can be applied to an output signal from the sensor to determine what location point in the reference coordinate system the output signal correlates to (and this is the sensed location point derived from the sensor output signal). If the sensed location point derived from the output signal is outside the predefined bounding space, then this indicates that an extrinsic magnetic field generator has entered the vicinity and therefore that an intruder may be attempting to tamper with the security system and an alert signal is generated to alert the user.

The predetermined bounding space may have been derived based on at least two output signals obtained from the sensor during a prior calibration process.

The prior calibration process may be a method according to any aspect of the calibration method described above.

Preferably the system is configured to operate in a monitoring mode, wherein the system only monitors for an extrinsic magnetic field generator when the system is in its monitoring mode. Other modes that the security system can run in including a standby mode or a calibration mode, the security system being run in calibration mode during calibration of the system.

According to a further aspect of the invention there is provided a program for carrying out any method of detecting if an extrinsic magnetic field generator has entered the proximity of a security system for a window or door assembly as described above.

According to a further aspect of the invention there is provided a security system for a window or door assembly, the security system comprising a first magnetic field generator, a first sensor for sensing a magnetic field, one of the first magnetic field generator and first sensor being mounted to a moveable element of the window or door assembly, the other being mounted to a reference structure that the moveable element is moveable relative to, the system further comprising a processing device configured to execute instructions to: receive an output signal from the sensor, the signal being associated with a measured magnetic field, derive a sensed location point corresponding to the output signal in a reference coordinate system, determine whether the sensed location point falls within a predetermined bounding space defined in the reference coordinate system, the predetermined bounding space having been derived based on at least one output signal obtained from the sensor during a prior calibration process; and generate an alert signal if the output signal falls outside the predefined bounding space.

The system suitably further comprises means for generating an alert if the output signal falls outside the predefined bounding space.

Preferably the system further comprises a magnetic proximity sensor, mounted to a moveable element of the window or door assembly or to a reference structure that the moveable element is moveable relative to.

The magnetic proximity sensor, such as a reed switch, provides back-up monitoring for the security system. The reed switch may be mounted to the leaf or to the frame of the door or window assembly.

Said magnetic proximity sensor has a normal state and an activated state, said magnetic proximity sensor converting to the activated state if a magnetic field is applied to the reed switch magnetic proximity sensor.

The magnetic proximity sensor is configured within the security system such that if an extrinsic magnet is brought into close proximity of the magnetic proximity sensor, the magnetic proximity sensor will convert to its activated state. This indicates that an extrinsic magnet has been brought into proximity of the sensor. The system is configured such conversion of the magnetic proximity sensor to its activated state will generate an alert signal. This system thereby providing an anti-tamper alert system.

According to a further aspect of the invention there is provided a security system for a window or door assembly, the security system comprising a first magnetic proximity sensor and corresponding proximity sensor magnet, and a second magnetic proximity sensor, each magnetic proximity sensor having a normal state and an activated state, each magnetic proximity sensor converting to the activated state if a magnetic field is applied to the magnetic proximity sensor, the first and second magnetic proximity sensors both being mounted to one of a moveable element of the window or door assembly and a reference structure that the moveable element is moveable relative to, the proximity sensor magnet being mounted to the other of the moveable element and reference structure at a position such that when the moveable element is positioned directly adjacent the reference structure, the first magnetic proximity sensor is caused to be in its activated state and the second magnetic proximity sensor remains in its normal state.

If an extrinsic magnet is brought into close proximity of the first and second sensors, both sensors will convert to their activated states. This indicates that an extrinsic magnet has been brought into proximity of the sensors, thereby providing an anti-tamper alert system.

If said magnetic proximity sensor is a mechanical magnetic switch, such as a reed switch, the magnetic proximity sensor will convert to its activated state by the applied magnetic field causing the switch to close (for a normally open type switch) or to open (for a normally closed type switch). If the magnetic proximity sensor is a solid state magnetic proximity sensors then the magnetic proximity sensor may be configured to convert to its activated state if a magnetic field above a predetermined value is detected. Said predetermined value may be a predetermined factory setting. In such cases the system preferably further comprises a processing device configured to receive output signals from the second magnetic proximity sensor to determine whether the magnetic field sensed is above said predetermined value. Applying a magnetic field to said magnetic proximity sensor or sensors refers to application of a magnetic field over and above the ambient magnetic

field.

Preferably the system further comprises means for generating an alert signal if both the first and second magnetic proximity sensors are transitioned to their activated state.

The system may comprise a plurality of magnetic proximity sensors. When the moveable element is positioned directly adjacent the reference structure, the first magnetic proximity sensor is caused to be in its activated state and the other magnetic proximity sensors remains in their normal state. The second and further magnetic proximity sensors may be arranged around the first magnetic proximity sensor. In such embodiments the system preferably further comprises means for generating an alert signal if the first magnetic proximity sensor and at least one of the other magnetic proximity sensors are transitioned to their activated states.

Preferably all of the magnetic proximity sensors are housed together in a single housing.

Preferably each magnetic proximity sensor is a reed switch. The magnetic proximity sensors in any of the embodiments in the present inventions may comprise other types of magnetic proximity sensor than reed switches or other types of mechanical magnetic switch. For example, solid state magnetic proximity sensors such as anisotropic magnetoresistive (AMR) sensors or Hall effect sensors may be employed as proximity sensors.

According to a further aspect of the invention there is provided a security system for a window or door assembly, the window or door assembly comprising a leaf moveable relative to a frame between closed and open positions, the security system comprising a magnetic proximity sensor mounted to the leaf or frame, said magnetic proximity sensor having a normal state and an activated state, said magnetic proximity sensor converting to the activated state if a magnetic field is applied to the magnetic proximity sensor, the system further comprising a processing device configured to receive output signals from the magnetic proximity sensor, the system further comprising means for generating an alert signal if said magnetic proximity sensor transitions to its activated state, the magnetic proximity sensor being positioned on the leaf or frame such that it does not align with any corresponding magnet on the other of the leaf or frame when the leaf is in its closed position.

In preferred embodiments said magnetic proximity sensor is a reed switch, but it may be any other type of magnetic proximity sensor such as a one, two or three axis magnetometer or an AMR sensor. In prior art systems reed switches are ordinarily positioned on the leaf or frame such that they align adjacently with a corresponding magnet on the other of the leaf or frame when the leaf is in its closed position, causing the reed switch to transition to its activated state as a means for detecting whether the leaf is open or closed. In the present invention however, since the magnetic proximity sensor does not align in close proximity with any magnet when the leaf is in its closed position, the magnetic proximity sensor will not transition to its activated state when the leaf is in its closed position. The magnetic proximity sensor is therefore configured as a sensor for detecting whether an extrinsic magnetic field generator has been brought into proximity with the magnetic proximity sensor and the system is therefore configured to detect whether an intruder is attempting to tamper with the system.

According to a further aspect of the invention there is provided a security system for a window or door assembly, the window or door assembly comprising a leaf moveable relative to a frame between closed and open positions, the security system being configured to detect whether the leaf is in its closed or an open position, the security system including a first sensor for detecting whether the leaf has been moved or knocked, the security system further being configured to generate an alert signal if the system detects that the leaf has been moved or knocked whilst in an open position.

By allowing activation of the sensor whilst the leaf is in its open position, the security system can detect whether the leaf has been moved or knocked whilst the leaf is open.

This means that the security system can be armed even when the leaf is insecure (i.e. if the leaf is open). Typically in prior art building security systems, the system would check whether each monitored door or window is open as part of the arming process and if a door/window is detected to be open, the system would provide an alert to the user that a particular door/window is open. This gives the user a chance to close the open door/window before they leave the building or they can alternatively arm the system without closing the door/window, in which case the sensor for that door/window will not have been activated and will not monitor security of that opening and the security system is only partially armed. In the present invention, the security system is adapted to allow monitoring of a window or door whilst that window or door is open. This means that a window or door may be left open (for example a window may be left open in night vent position in order to air a building on a hot day) and the security system may nevertheless be fully armed to monitor every opening at which a sensor is located.

Preferably the system further comprises a processing device configured to execute instructions to allow arming of said sensor whilst the leaf is in an open position.

Preferably said first sensor is adapted for sensing a magnetic field.

In some embodiments said sensor is a three axis magnetometer. Preferably said magnetometer is mounted to the leaf. In some embodiments the system further comprises a first magnetic field generator, one of said magnetic field generator and sensor for sensing a magnetic field being mounted to the leaf and the other being mounted to the frame.

In other embodiments said first sensor is a vibration sensor. Preferably said vibration sensor is an accelerometer.

In alternative embodiments said first sensor may be a rotary encoder.

In some preferred embodiments the security system is adapted for monitoring the security of a window having a friction hinge. For example, the sensor, or any sensed element sensed by the sensor, is mounted to the leaf of a window, the leaf being coupled to the frame by a friction hinge assembly.

Preferably the security system further comprises a window assembly comprising a leaf moveable relative to a frame between closed and open positions, the window assembly comprising a friction hinge assembly coupling the leaf to the frame.

The friction hinge (also known as a friction stay) frictionally retains the leaf in an open position unless a force above a predetermined level is applied to move the sash from that open position. Additional force is therefore required to overcome the friction means. Frictional resistance is provided by the friction hinge so as to retain the window in a desired position, even when exposed to small forces, such as those created by the wind.

According to a further aspect of the invention there is provided a method of operating a security system for monitoring at least one window or door assembly, said window or door assembly comprising a leaf moveable relative to a frame between closed and open positions, the security system comprising means for detecting whether the leaf is in its closed position or an open position, the security system including a first sensor for detecting whether the leaf has been moved or knocked, the method comprising: arming said first sensor whilst the leaf is in an open position.

Preferably the method comprises arming said first sensor whilst the leaf is in an open position.

According to a further aspect of the invention there is provided a program for carrying out any method of operating a security system for monitoring at least one window or door assembly as described above.

A program may be provided for carrying out any method as described herein.

The security systems of the present invention preferably comprise wireless transmission means. The security systems of the present invention preferably comprise a first user interface. The security systems of the present invention preferably comprise a memory.

The security systems of the present invention may further comprise a leaf moveable relative to a frame between closed and open positions.

The sensor in any of the embodiments disclosed herein may be a one, two or three axis magnetometer.

References herein to magnetometers may be to a one, two or three axis magnetometer. It will be understood that the terms leaf and sash can be used interchangeably.

It will be understood that the terms processing device, processing means and processor can be used interchangeably.

References herein to mounting of any first element to any second element encompass direct or indirect mounting (e.g. the mounting of the first element to a third element which is mounted to the second element).

The phrase in communication with" means "able to transmit signals to and/or receive signals from.' It is to be understood that the mere use of the term "first" does not require that there be any "second," and the mere use of the term "second" does not require that there be any "third," etc.

Brief Description of the Drawinos

Embodiments of the invention will now be described by way of example only, with reference to the accompanying drawings, in which: Figure 1 shows a prior art system 10 for detecting whether a door/window is open or closed; Figures 2A to 2E illustrate diagrammatically a system and method for calibrating a security system according to one aspect of the invention; Figure 2A shows a security system according to an embodiment of the invention; Figure 2B shows diagrammatically boxes that may be defined in a reference coordinate system; Figure 2C shows a graphical representation of a set of bounding shapes that have been defined in a reference coordinate system; Figure 2D shows a basic flow diagram illustrating a method for calibrating the security system; Figure 2E is a functional block diagram showing some of the elements of the security system; Figure 2F shows a sensor module for the security system of Figure 2A; Figure 3 shows a security system according to a further embodiment for use in detecting possible tampering with the security system; Figure 4A shows a system for detecting whether an extrinsic magnetic field generator has entered the proximity of the security system; Figure 4B shows a sensor module for the system of Figure 4A; Figure 4C shows an alternative sensor module for the system of Figure 4A; Figure 5 shows a security system allowing arming of a sensor for monitoring a window/door when the window/door is open.

Description of the Preferred Embodiments

The present embodiments represent currently the best ways known to the applicant of putting the invention into practice. But they are not the only ways in which this can be achieved. They are illustrated, and they will now be described, by way of example only. Common features between the assemblies of the different figures are referenced by common reference numerals.

Figure 1 shows a prior art system 10 for detecting whether a door/window is open or closed via a contact detection system. The prior art system employs a reed switch magnet 11 mounted to the moveable leaf 12 of a window and a reed switch 13 mounted to the window frame 14 (the reed switch magnet 11 and reed switch 13 may of course be mounted the other way around). Such prior art systems may be armed when the two parts (the reed switch and the reed switch magnet) come into close proximity with each other, indicating that the leaf is shut, which allows signalling to an alarm (i.e. a wider burglar alarm system) to switch on (i.e. to allow monitoring of the open/closed state of the window). These systems do not know whether the window has actually been locked, only that the leaf and frame are together. The reed switch is a very simple sensor which can be activated by any generic magnet. As discussed above, reed switch assemblies are therefore vulnerable to tampering using an extrinsic magnet.

Other devices employed in prior art security systems include vibration sensors to detect hard knocks on a door/window that could indicate someone is attacking the door/window and to signal an alert (e.g. an alarm to sound or a notification to be sent to the homeowner). As with reed switch assemblies, a vibration sensor cannot detect whether a window/door has actually been locked, only whether a vibration has been sensed. Also, as with reed switch assemblies, vibration sensors in prior art systems can typically only be armed when the window/door has been closed.

Figures 2A to 2F illustrate diagrammatically a system and method for calibrating a security system according to an aspect of the invention. Some of the basic elements of the security system are shown in Figure 2A. The security system 100 comprises a first sensor 110 and a magnetic field generator 120. One of the pair is mounted to the leaf 12 of an openable door/window and the other is mounted to the frame 14. In the embodiment in Figure 2A the magnetic field generator 120 is mounted to the leaf and the sensor 110 to the frame, but it will be understood that they could be mounted the other way around. The sensor and magnet assembly shown in Figure 2A may be part of a wider security system for monitoring a plurality of windows and/or doors. For example, a sensor and magnet pairs may be mounted at each of a number of external windows/doors of a property.

The sensor 110 in this embodiment and in other embodiments described herein is preferably a magnetometer, which in preferred embodiments is a three axis magnetometer that is able to detect the position of the corresponding magnet in three coordinate axes. The three axis magnetometer will therefore output the sensed X, Y, and Z components of the magnetic flux vector present at the magnetometer. Two or one axis magnetometers may be employed instead however.

In preferred embodiments the sensor 110 is housed in a sensor module 121, as shown diagrammatically in Figure 2F, the sensor module 121 comprising a housing 122 which contains the magnetometer 110, means to power the sensor such as a battery or batteries 123, and a communications module 124. The sensor module may also include a basic processor. The communications module allows output signals from the sensor to be transmitted wirelessly to a central processing device. The communications module may comprise RE transmissions means such as those using Bluetooth, Zigbee or WiFi communications standards for example. Output signals from the sensor 110 are received by a central processing device, which may be a dedicated processing device or may be a server, computer, or a mobile communication device for example.

The central processing device is configured to execute instructions involved in calibration of the security system ready for use in security monitoring, the instructions being defined by programming instructions (such as a software or firmware program), which may be stored in a memory. The calibration method involves setting authorised magnetic field spaces, as will now be described.

The system is operated in calibration mode initially when setting up the system and a monitoring mode when the system is being monitored. Figure 2D is a basic diagram illustrating the basic initial steps for calibrating the system. At 300, in order to calibrate the system the user places the system into calibration mode by providing a signal to a processor 24 using a user interface 23 (see also the schematic diagram in Figure 2E). In such embodiments, the system has a user interface for providing a signal to a processor within the sensor module to enter the calibration mode. Such a user interface may comprise a push button or a remote device with keypad or touchscreen etc such as a smartphone. Alternatively, the calibration mode may be entered automatically after a battery is first installed and/or when the sensor module switched on for the first time. Once the system is in calibration mode, at 301 the user is prompted by the system to position a moveable element (which in this case is the leaf 12) in a first predetermined position, such as a closed position, or an open position, via the user interface or some other indicator means. After the user has placed the leaf in the first predetermined position, at 302 the user provides an indication to the processor 24 via the user interface 23 that the leaf has been placed into the first predetermined position. Alternatively the indication that the leaf is in the predetermined position may be automatically derived by the system by determining that the magnetic field sensed by the magnetometer has been stable for a predetermined time period. At 303, the processor 24 then records one or more properties of the magnetic field produced by the magnet 120 as sensed by the magnetometer 110 and stores at least one of the properties or values derived therefrom in a memory 25. At 304-306, after the system has registered the leaf in the first predetermined position the steps repeat in relation to a second predetermined position as shown in Figure 2D.

Registering the leaf in one or two predetermined positions may be sufficient to calibrate the system, or registration in a third or further predetermined positions may be required, in which case the steps would be repeated for the further predetermined position(s). The leaf may be moved and registered in a series of different predetermined positions as part of the process of calibrating the system. For example, a hinged leaf may be registered in the closed position, a night vent / slightly open position and a 90 degree open position etc. The method of calibrating the security system is preferably an in-situ method of calibrating the security system (i.e. a method of calibration on location). The calibration steps are carried out with the magnetic field generator and sensor installed in the location at which they will be monitoring. In other words, during calibration the moveable element is moved and the corresponding output signals of the sensor are recorded after the window or door assembly has been installed in a building at a particular geographical location. This contrasts from security systems which are set up ready for use during fabrication in a factory and prior to installation in a building.

The software executes instructions to derive, from the stored magnetometer output readings from registration of the sensor in each predetermined position, a corresponding location point in a reference coordinate system. The corresponding location point in the reference coordinate system may also be referred to as a magnet field point. The reference coordinate system is a virtual coordinate system, in which a location, for example defined by a Cartesian coordinate, is assigned to each output reading stored from registration of the leaf in each predetermined configuration.

Using each said location point, a bounding space is then defined in the reference coordinate system, each of said location points being within the bounding space. In preferred embodiments, the bounding space in the virtual coordinate system is determined by forming around each said location point derived from the sensor output readings a bounding shape or bounding form, preferably in the shape of a box or cube. The system may be adapted to define a larger set of location points in the reference coordinate system that the magnet may move through during full movement of the leaf from its closed position to a fully open position (or from any predetermined first position to any predetermined second position) via interpolation from a small set of location points derived from registration of the leaf in a small set of predetermined states. A bounding form may be defined for each such location point, whether derived via manual registration or interpolation by the system.

A series of bounding forms that have been linked up to create a larger space in the reference coordinate system may be referred to as a bounding space. This linking up of a series of bounding forms to create a larger space may be referred to as tunnelling. A graphical representation of a set of bounding forms 201 in the reference coordinate system 200 is shown in Figure 2C. Figure 2C is a graphical representation of the movement of magnetic coordinates captured in realtime and the corresponding bounding forms. The axes indicate measured magnetic field in Gauss, which corresponds to locations in the reference coordinate system. Each bounding space may be classified to correspond to a particular state of the leaf. This will now be described in the context of a tilt and turn window. Tilt and turn windows are well known and typically allow the window to be tilted open for secure ventilation by rotation of the handle by 90 degrees from its closed position (or by 180 degrees for certain tilt and turn handles) and also allow the window to be turned inwards by rotation of the handle 180 degrees from its closed position. These states may be referred to as 'closed', 'tilted' or 'turned' respectively. When the leaf is in its tilted or turned state, the leaf may move through a continuous range of positions within that particular state. In order to capture this range of movements, corresponding bounding forms around a series of discrete location points within that state are linked to create a larger bounding space corresponding to that particular state of the leaf. For example, for a tilt and turn window, the tilted state would include the range of movements of the handle being rotated by 90 degrees and the leaf travelling from a vertical position to a tilted angle. The bounding space labelled 201 in Figure 2C represents this tilted state for a window in which one of the magnet-sensor pair is mounted to the handle, such that it moves through different positions as the handle is being rotated and when the leaf is being tilted/turned. The bounding space labelled 202 represents the handle rotated to the 'turned' position, while the window is still vertical and in its closed position. The bounding space labelled 203 represents a state in which the handle is in its closed position and the window is closed and locked.

If calibrating the system to capture a path of movement of the moveable element, the method steps may differ slightly from that shown in Figure 2D in that the user will be prompted to move the moveable element from a first predetermined position to a second predetermined position, but rather than merely recording magnetic field properties at each predetermined position, the system will record magnetic field properties captured along the path of movement in order to generate a set of bounding forms in the reference coordinate system corresponding to the particular path of movement. The calibration method may include the defining of at least one bounding space in the reference coordinate system, the or each bounding space corresponding to a predetermined path of movement of the moveable element or to a predetermined position of the moveable element. The method need not include separate individual prompts to the user to position the moveable element at each predetermined position. Instead the user may simply be instructed to move the moveable element through a predetermined sequence of movements.

Once the system has been calibrated, the security system may be armed to monitor and determine the position of the leaf relative to the reference structure if the leaf is moved. By defining bounding shapes around a plurality of location points in a virtual reference coordinate system, each location point corresponding to a position that a moveable element may occupy in real space, this allows lower cost magnetometers to be used in the security system. Whilst high cost magnetometers allow very accurate determination of relative position of a magnet, the defining of bounding shapes in the reference coordinate system allows account to be taken of noise, such as digital noise and environmental factors such as temperature, which could affect the output signal from the sensor, allowing lower cost magnetometers to be used in the system.

The calibration steps are preferably carried out in-situ (i.e. carried out with the magnet 120 and sensor 110 mounted to a door/window that is installed in a building). During this calibration process, readings are taken from the sensor 110 when the leaf is in various positions or states. From each reading (which is a single point in 3D space), a bounding form or box of predetermined size is generated to account for mechanical deviations and noise. The size of the box may be based on the position that the leaf is in and the distance of that position from other coordinate points that have been captured. Each box forms a

calibrated magnetic field space.

Once all of the data for the interested states have been captured and the boxes have been defined, these boxes form protected regions for all movement of the window/door i.e. the output from normal movement of the leaf should lie within all of the calibrated boxes. Via calibration in this way, precise movements of a door or window may be detected.

In other embodiments one of the magnet-sensor pair may be mounted to a moveable element of the window / door assembly other than directly mounting to the leaf itself. For example, one of the magnet-sensor pair may be mounted to the handle of a door/window.

If set up in this way, the system may be used to determine whether the handle is open or closed and whether the leaf is closed, open and at what angle the leaf is open relative to the frame (since the handle moves as the leaf moves). The security system would be calibrated in the same way as described above, with the output signals being registered when the magnet 120 is at various positions, such as handle closed, handle open, leaf open etc and bounding shapes would be defined in the reference coordinate system for each location point derived from the sensor output signals. In other embodiments, one of the magnet-sensor pair may be mounted to the slideable drive rail of an espagnolette locking mechanism of a door/window. If set up in this way, the system may be used to determine whether the door/window is locked or unlocked and whether the leaf is closed, open and to what angle the leaf is open relative to the frame (since the drive rail moves as the leaf moves). The processing device runs an algorithm configured to detect subtle movements of the one of the sensor-magnet pair that is mounted to the moveable element, so that the status of the window / door assembly can be monitored. The dedicated software monitors the magnetic field changes sensed in order to monitor the position of the moveable element in realtime.

For a magnet-sensor pair set up for use with a casement window with an espagnolette locking mechanism wherein one of the magnet-sensor pair is mounted to the handle or drive rail and the other to the frame, the predetermined configurations that the window would preferably be registered in during calibration are: - Leaf closed and locked - Handle open (i.e. leaf unlocked) -this configuration may be termed "marginally open" - Leaf in night-vent position (defined by a night vent keep mounted to the frame for receiving a locking element mounted to the leaf, in order to maintain the leaf at a position which is slightly open to allow ventilation) -this configuration may be termed "airmode" - Leaf open beyond night-vent position -this configuration may be termed simply "open" Figure 2B shows diagrammatically boxes that may be defined in the reference coordinate system for each of these configurations, wherein the boxes may be of different sizes depending on the state of the window being registered. The configurations shown are leaf closed 210, marginally open 211, airmode 212 and leaf open 213. It has been found that registering in these positions provides data to define a kinematic model of the relative movement of the magnet-sensor pair in the coordinate system to be able to accurately monitor the configuration of the window.

The user may interact with the system via an application stored on a computing device, for example a mobile computing device, such as mobile telephone or tablet computer. This may be a dedicated application for use in calibrating the system and monitoring the status of windows/doors.

The calibration method may include a step of using at least one characteristic relating to the window or door assembly as an input in determining the calibration parameters for determining the position of the moveable element from the output signals from the sensor. The characteristic may be the type of window or door assembly (e.g. casement window, tilt and turn window) or a dimension of the leaf. For a casement window, the dimension of the leaf from the hinged edge to the edge that engages the jamb may be input into the system for example. Input of such a dimension assists in extrapolating expected output values of the sensor when the leaf is at or near a fully open position, even if the leaf was not registered at such an extent of opening during the calibration process. The leaf characteristic may be input via the user interface. This may be done for example by the user inputting a reference code associated with the particular model of window into the user interface. In such embodiments the system includes a database or library accessible by the processing device containing records having the reference code and corresponding calibration parameter adjustments indexed therein for each type of leaf. This means that the same system can more easily be used with different sizes of leaf.

The calibration of the security system can be set up to take account of magnetic drift.

Magnetic drift also known as polar drift is a geological phenomenon caused by variations in the flow of molten iron in Earth's outer core, resulting in changes in the orientation of Earth's magnetic field, and hence the position of the magnetic north-and south poles. The North Magnetic Pole is approximately 965 kilometres (600 mi) from the geographic north pole. The pole drifts considerably each day, and since 2007 it moves about 55 to 60 km (34 to 37 mi) per year as a result of this phenomenon. The South Magnetic Pole also is constantly shifting due to changes in the Earth's magnetic field.

The processing device is programmed to execute instructions to periodically auto self-recalibrate itself to account for the earth's magnetic drift by taking for example the originally recorded positioning data from a closed position and then adding or deducting any new magnetic drift data to the originally taken positioning data. This ensures accuracy of positioning data and reporting. For example, on a particular day (Day 1), the known calibrated state data value when closed may be 0001. On a Day 2, when the unit is closed a new data value is recorded of 0001.1. The system would then auto-calibrate by adding the polar drift data value difference to all recorded known states (i.e. by adding 0000.1 to all positions.

It will be understood that one of the magnet-sensor pair may be mounted to any moveable element to be monitored and the other to a reference structure that the moveable element moves relative to. In preferred embodiments the moveable element is the leaf of a window/door, in which case the sensor/magnet may be mounted directly to the leaf or to a moveable element on the leaf, such as a handle or drive rail of an espagnolette mechanism and the other of the sensor/magnet may be mounted to the frame that the leaf moves relative to. The reference structure may of course be any support structure that the moveable element moves relative to, such as the leaf, frame, a wall, or other suitable structure as may be suitable for the particular embodiment in question.

Existing security systems that employ reed switches to monitor doors and windows are very vulnerable to tampering by intruders as any off the shelf generic magnet placed close to a reed switch will provide a false reading to the monitoring system indicating that the door/window is closed. This allows an intruder to break in through a door/window without triggering the alarm by simply placing or affixing a magnet adjacent the reed switch.

The inventor has realised that by calibrating a system including a first magnetic field generator and sensor comprising magnetometer, such as a three axis magnetometer, to set authorised magnetic field spaces in a reference coordinate system as described above, the system can be used to detect whether any unauthorised magnets have been brought into the proximity of the magnetometer (i.e. brought within or well within the magnetometer's range of detection), as will now be described.

After the system has been calibrated as described above, it can be armed to operate in a monitoring mode. Once in monitoring mode, any changes in the magnetic field sensed by the magnetometer will be transmitted as output signals from the magnetometer to the processing device. The processing device applies the calibration parameters established during the calibration process to an output signal from the sensor to determine a location point in the reference coordinate system that the output signal correlates to. If the location point derived from the output signal is inside the predefined bounding space, then this indicates that the moveable element has been moved along its normal path of movement (for example the leaf moving between closed and open positions) and the output signal is within a predefined range of measurement tolerance. If the location point derived from the output signal is outside the predefined bounding space, then this indicates an anomalous magnetic field reading, suggesting that an extrinsic magnetic field generator has entered the vicinity and therefore that an intruder may be attempting to tamper with the security system. An alert signal is therefore generated to alert the user via a status indicator 26 of some sort (see Figure 2E).

The system has means for generating an alert signal in response to detection of an extrinsic magnetic field generator in the vicinity of the sensor. The alert signal may cause at least one of the following to be activated (i) an audible alarm; (ii) a light; (hi) notification on a remote user display means (e.g. via SMS, email, notification through a dedicated application etc).

A security system which can monitor the position of a moveable element of a window or door assembly whilst also detecting possible tampering by extrinsic magnetic field generators is shown in Figure 3. The security system 101 has a magnet 120 mounted to the leaf 12 and a magnetometer 110 mounted to the frame 14. Further back up monitoring can be provided by mounting a magnetic proximity sensor such as a reed switch 130 to the frame 14, the reed switch being in communication with the processing device 24. The reed switch 130 may be any standard proximity switch which is activated/deactivated by an applied magnetic field. For example, the reed switch may be a normally open (NO) type or a normally closed (NC) type reed switch. Usually a reed switch would be paired with a reed switch magnet on the other of the leaf and frame to which the reed switch is mounted, however in this case, for back up monitoring, only a reed switch is needed. If an extrinsic magnetic field generator such as an unauthorised magnet is brought into proximity of the security system, not only will the system detect this due to the prior calibration process as described above, but the reed switch will also be activated to switch to the opposite state from that which it is normally in, indicating that a magnet has been brought into proximity of the security system. The system is configured to generate an alert signal if the reed switch is converted to its activated state.

Instead of being mounted to the frame 14 as shown in Figure 3, the reed switch 130 may be mounted to the leaf 12.

Referring to Figures 4A to 4C, a further example of a tamper proof security system is shown. Referring to Figure 4A, the security system comprises a sensor module 132 mounted to the frame 14 and a reed switch magnet 131 mounted to the leaf. In other embodiments the sensor module could be mounted to the leaf and the reed switch magnet to the frame. Referring to Figure 4B, the sensor module 132 comprises a first reed switch 134 and a second reed switch 136 within a sensor module housing 137. Each reed switch 134, 136 has an activated state which it enters if a magnet is placed in close proximity to it and a normal state. Both reed switches 134, 136 may be normally open (NO) type or a normally closed (NC) type reed switches or they may be one of each type.

The reed switch magnet 131 and sensor module 132 are mounted relative to one another such that when the leaf is closed, the magnet 131 is aligned with the first reed switch 134, so as to activate the first reed switch 134 to convert to its activated state. The second reed switch 136 is positioned relative to the first reed switch 134 and the reed switch magnet 131 such that the second reed switch 136 remains in its normal state when the leaf is closed. By positioning the second reed switch 136 by at least a sufficient spacing (such as at least around 10 mm away) from the first reed switch 134, the reed switch magnet 131 can be aligned with the first reed switch 134 such that the second reed switch 136 does not convert to its activated state even when the reed switch magnet 131 is adjacent the first reed switch 134 when the leaf is closed.

If an extrinsic magnetic field generator (such as an uncalibrated magnet) is brought into close proximity with the sensor module 132, both of the first and second reed switches 134, 136 are activated. Both the first and second reed switches are in communication with a processing device which is configured to generate an alert signal if both of the first and second reed switches 134, 136 are activated. The alert signal may cause at least one of the following to be activated (i) an audible alarm; (ii) a light; (iii) notification on a remote user display means (e.g. via SMS, email, notification through a dedicated application etc). This indicates to the user that an intruder is attempting to tamper with the sensor module 132 using an extrinsic magnet.

One or more additional reed switches may be incorporated with the first reed switch 134 in the sensor module. Figure 40 shows a further example of a sensor module 132' that may be used in the system of Figure 4A, the sensor module 132' having a plurality of additional reed switches 136'. The sensor module 132' comprises a first reed switch 134 and a plurality of further reed switches 136' within a sensor module housing 137'. In this embodiment four additional reed switches 136' are present in addition to the first reed switch 134, but it will be understood that any number of reed switches may be incorporated into the sensor module in addition to the first reed switch 134.

Each reed switch 134, 136 has an activated state which it enters if a magnet is placed in close proximity to it and a normal state. The reed switches 134, 136 may all be normally open (NO) type or a normally closed (NC) type reed switches or one or more may be NO type and the other(s) the NC type.

As with the embodiment of Figure 4B, the reed switch magnet 131 and sensor module 137' are mounted relative to one another such that when the leaf is closed, the reed switch magnet 131 is aligned with the first reed switch 134, so as to activate the first reed switch 134 to convert to its activated state. The additional reed switches 136' are all positioned relative to the first reed switch 134 and the reed switch magnet 131 such that the second additional reed switches 136' remains in their normal state when the leaf is closed. By positioning the additional reed switches 136' by at least a sufficient spacing (such as each being at least around 10 mm away) from the first reed switch 134, the reed switch magnet 131 can be aligned with the first reed switch 134 such that the additional reed switches 136' do not convert to their activated even when the reed switch magnet 131 is adjacent the first reed switch 134 when the leaf is closed. All of the reed switches (the first reed switch 134 and the additional reed switches 136' are in communication with a processing device which is configured to generate an alert signal if any of the additional reed switches 136' are activated. Activation of one or more of the additional reed switches 136' indicates that an intruder is attempting to tamper with the sensor module using an extrinsic magnet.

The additional reed switches 136' are arranged around the first reed switch 134, each of the additional reed switches 136' being sufficiently spaced away from the first reed switch 134 such that, absent any extrinsic magnet being used to tamper with the assembly, when the leaf is closed the reed switch magnet activates the first reed switch 134 but does not activate the additional reed switches 136. For example, the additional reed switches 136' may be arranged in a ring or other shape around the first reed switch 134.

By including a plurality of additional reed switches, each of which is not activateable by the reed switch magnet in the sensor module in addition to the first reed switch which is activateable by the reed switch magnet, the sensor module is even more effective in detecting if an extrinsic magnetic field generator (such as an uncalibrated magnet) is brought into close proximity with the sensor module 132.

In the above embodiments which employ one or more reed switches, any magnetic proximity sensor(s) may be used in place of the reed switch(es). For example, other types of mechanical magnetic switch may be used in place of reed switches. Alternatively, solid state magnetic proximity sensors may be employed such as anisotropic magnetoresistive (AMR) sensors or Hall effect sensors.

Both prior art reed switch assemblies and vibration sensors can only be activated to monitor a window/door during arming of a security system if the window/door that the sensor is mounted at is closed when the system is being armed. Typically in prior art building security systems, the system would check whether each monitored door or window is open as part of the arming process and if a door/window is detected to be open, the system would provide an alert to the user that a particular door/window is open. This gives the user a chance to close the open door/window before they leave the building; alternatively the user has the option of arming the security system without closing the door/window, in which case the sensor for that door/window will not have been activated and will not monitor security of that opening; in such a situation the security system is therefore only partially armed. This creates a problem for hot days, if a user wishes to leave a window open in the night vent position in order to air the building for example. If the user only partially arms the security system, then this leaves the building with a vulnerable access point to the building.

Referring to Figure 5, a further embodiment of a security system 103 according to an aspect of the present invention is shown. The security system 103 comprises a first sensor 111. In the embodiment shown in Figure 5, the first sensor 111 is a magnetometer and it is mounted to the leaf 12 of a window or door, however the system may be configured in other ways, as will be described. The security system includes a processor 24 configured to execute instructions that allow monitoring of the leaf 12 whilst the leaf is open (for example to monitor whether the leaf has moved).

The security system is configured such that during arming of the security system the system determines whether the leaf 12 is closed or open. This may be done by means of the system incorporating any suitable means for determining whether the leaf is closed or not, such as a reed switch and corresponding magnet pair or a calibrated security system as shown in the embodiment of Figure 2A. During arming, if the leaf 12 is open, this will be indicated to the user via a user interface 23. The user then has the option to decide whether they wish to close the leaf 12 before they finish arming the security system or to activate the first sensor 111, which the user can do so via the user interface 23. If the user selects via the user interface for the first sensor 111 to be activated despite the leaf 12 being open, the first sensor 111 is activated (and any other sensors in the security system are activated also) in order to arm the security system. Once the security system is armed in this way, if the leaf 12 is subsequently moved, for example if an intruder attempts to access the property by opening the leaf 12 further, this is detected and an alert signal is generated to alert the user. This means that a user can leave a window open, yet still arm the corresponding sensor at that window to monitor the window, giving peace of mind. The first sensor 111 preferably comprises any sensor suitable for detecting whether the leaf has been moved or knocked. The sensor 111 may be a magnetometer (e.g. a one, two or three axis magnetometer) for example.

As with previous embodiments, the system has means for generating an alert signal. The alert signal may cause at least one of the following to be activated (i) an audible alarm; (ii) a light; (iii) notification on the user interface 23.

This type of security system is particularly suited to windows mounted to their frame via a friction hinge 15, as shown in the example in Figure 5, which are unlikely to move if left open except if tampered with by an intruder. The security system 103 may of course be used with windows/doors that are not mounted via a friction hinge however.

In alternative embodiments the first sensor 111 may be mounted on the frame 14 or to a wall or other suitable fixed support structure near the leaf 12. In such an embodiment a magnetic field generator is mounted to the leaf 12, such that the magnetometer can detect if the leaf moves.

In other embodiments the first sensor comprises a vibration sensor, such as an accelerometer, mounted to the leaf 12. If the vibration sensor is armed as described above, the vibration sensor can be activated, even when the leaf is open, to monitor whether the leaf is knocked. Vibration of the leaf via a knock is likely to be the result of an intruder trying to gain access to the building. If vibration of the leaf is detected, the system generates an alert signal. The security system may comprise a vibration sensor mounted to the leaf instead of the magnetometer-sensor pair shown in Figure 5, or in addition to the magnetometer-sensor pair shown in Figure 5.

In other embodiments the first sensor of security system 103 is a rotary encoder. The rotary encoder may be mounted to a rotating shaft of a door drive, for example for a powered door, for monitoring the extent to which the leaf is open. If the rotary encoder detects movement of the leaf, then the system generates an alert signal.

It is to be appreciated that, although the invention has been described hereabove with reference to certain examples or embodiments of the invention, various additions, deletions, alterations and modifications may be made to those described examples and embodiments without departing from the intended spirit and scope of the invention.

Claims

Claims 1. A method of calibrating a security system for a window or door assembly, the security system comprising a first magnetic field generator and a first sensor for sensing a magnetic field, one of the first magnetic field generator and first sensor being mounted to a moveable element of the window or door assembly, the other being mounted to a reference structure that the moveable element is moveable relative to, the method comprising receiving an output signal from the sensor when the moveable element is in a first position, using said output signal to derive a location point in a reference coordinate system corresponding to said position of said moveable element, and defining at least a first bounding space in the reference coordinate system, said location point being within the bounding space.
2. A method of calibrating a security system for a window or door assembly according to claim 1, wherein the method is carried out in-situ.
3. A method of calibrating a security system for a window or door assembly according to claim 1 or 2, wherein an output signal from the sensor is received when the moveable element is in each of a plurality of positions and a location point in a reference coordinate system is derived from the output signal corresponding to each said position.
4. A method of calibrating a security system for a window or door assembly according to any preceding claim, wherein the step of defining at least a first bounding space in the reference coordinate system comprises defining a bounding form around each location point in the reference coordinate system that has been derived from an output signal of the sensor, each location point falling within its corresponding bounding form.
5. A method of calibrating a security system for a window or door assembly according to claim 1, wherein each bounding form comprises a cuboid shape.
6. A method of calibrating a security system according to any preceding claim, wherein the method further comprises the step of recalibrafing the security system to takeaccount of changes in the Earth's magnetic field.
7. A program for carrying out a method according to any of claims 1 to 6.
8. A security system for a window or door assembly, the security system comprising a first magnetic field generator and a first sensor for sensing a magnetic field, one of the first magnetic field generator and first sensor being mounted to a moveable element of the window or door assembly, the other being mounted to a reference structure that the moveable element is moveable relative to, the system further comprising a processing device configured to execute instructions to: receive an output signal from the sensor when the moveable element is in a first position, use said output signal to derive a location point in a reference coordinate system corresponding to said position of said moveable element, and define at least a first bounding space in the reference coordinate system, said location point being within the bounding space.
9. A security system for a window or door assembly, the security system comprising a first magnetic field generator and a first sensor for sensing a magnetic field, one of the first magnetic field generator and first sensor being mounted to a moveable element of the window or door assembly, the other being mounted to a reference structure that the moveable element is moveable relative to, the system further comprising a processing device configured to execute instructions to: receive an output signal from the sensor when the moveable element is in a first position, use said output signal to derive a location point in a reference coordinate system corresponding to said position of said moveable element, and define at least a first bounding space in the reference coordinate system, said location point being within the bounding space, the system being adapted for calibration using a method of any of claims 1 to 6.
10. A method of detecting if an extrinsic magnetic field generator has entered the proximity of a security system for a window or door assembly, the security system comprising a first magnetic field generator and a first sensor for sensing a magnetic field, one of the first magnetic field generator and first sensor being mounted to a moveable element of the window or door assembly, the other being mounted to a reference structure that the moveable element is moveable relative to, the method comprising receiving an output signal from the sensor, the signal being associated with a measured magnetic field, deriving a sensed location point corresponding to the output signal in a reference coordinate system, determining whether the sensed location point falls within a predetermined bounding space defined in the reference coordinate system, the predetermined bounding space having been derived based on at least one output signal obtained from the sensor during a prior calibration process; and generating an alert signal if the sensed location point falls outside the predefined bounding space.
11. A method of detecting if an extrinsic magnetic field generator has entered the proximity of a security system for a window or door assembly according to claim 10, wherein the prior calibration process comprises a method according to any of claims 1 to 6.
12. A method of detecting if an extrinsic magnetic field generator has entered the proximity of a security system for a window or door assembly according to claim 10 or 11, wherein the system is configured to operate in a monitoring mode, wherein the system only monitors for an extrinsic magnetic field generator when the system is in its monitoring mode.
13. A program for carrying out a method according to any of claims 10 to 12.
14. A security system for a window or door assembly, the security system comprising a first magnetic field generator, a first sensor for sensing a magnetic field, one of the first magnetic field generator and first sensor being mounted to a moveable element of the window or door assembly, the other being mounted to a reference structure that the moveable element is moveable relative to, the system further comprising a processing device configured to execute instructions to: receive an output signal from the sensor, the signal being associated with a measured magnetic field, derive a sensed location point corresponding to the output signal in a reference coordinate system, determine whether the sensed location point falls within a predetermined bounding space defined in the reference coordinate system, the predetermined bounding space having been derived based on at least one output signal obtained from the sensor during a prior calibration process; and generate an alert signal if the output signal falls outside the predefined bounding space.
15. A security system according to claim 14, wherein the system further comprises a magnetic proximity sensor, mounted to a moveable element of the window or door assembly or to a reference structure that the moveable element is moveable relative to.
16. A security system for a window or door assembly, the security system comprising a first magnetic proximity sensor and corresponding proximity sensor magnet, and a second magnetic proximity sensor, each magnetic proximity sensor having a normal state and an activated state, each magnetic proximity sensor converting to the activated state if a magnetic field is applied to the magnetic proximity sensor, the first and second magnetic proximity sensors both being mounted to one of a moveable element of the window or door assembly and a reference structure that the moveable element is moveable relative to, the proximity sensor magnet being mounted to the other of the moveable element and reference structure at a position such that when the moveable element is positioned directly adjacent the reference structure, the first magnetic proximity sensor is caused to be in its activated state and the second magnetic proximity sensor remains in its normal state.
17. A security system according to claim 16, wherein the system further comprises means for generating an alert signal if both the first and second magnetic proximity sensors are transitioned to their activated state.
18. A security system according to claim 16 or 17, wherein all of the magnetic proximity sensors are housed together in a single housing.
19. A security system according to any of claims 15 to 18, wherein each magnetic proximity sensor is a reed switch.
20. A security system for a window or door assembly, the window or door assembly comprising a leaf moveable relative to a frame between closed and open positions, the security system comprising a magnetic proximity sensor mounted to the leaf or frame, said magnetic proximity sensor having a normal state and an activated state, said magnetic proximity sensor converting to the activated state if a magnetic field is applied to the magnetic proximity sensor, the system further comprising a processing device configured to receive output signals from the magnetic proximity sensor, the system further comprising means for generating an alert signal if said magnetic proximity sensor transitions to its activated state, the magnetic proximity sensor being positioned on the leaf or frame such that it does not align with any corresponding magnet on the other of the leaf or frame when the leaf is in its closed position.
21. A security system for a window or door assembly, the window or door assembly comprising a leaf moveable relative to a frame between closed and open positions, the security system being configured to detect whether the leaf is in its closed or an open position, the security system including a first sensor for detecting whether the leaf has been moved or knocked, the security system further being configured to generate an alert signal if the system detects that the leaf has been moved or knocked whilst in an open position.
22. A security system according to claim 21, wherein the system further comprises a processing device configured to execute instructions to allow arming of said sensor whilst the leaf is in an open position.
23. A security system according to claim 21 or 22, wherein said first sensor is adaptedfor sensing a magnetic field.
24. A security system according to any of claims 21 or 22, wherein said first sensor is a vibration sensor.
25. A security system according to any of claims 21 to 24, wherein the security system further comprises a window assembly comprising a leaf moveable relative to a frame between closed and open positions, the window assembly comprising a friction hinge assembly coupling the leaf to the frame.
26. A method of operating a security system for monitoring at least one window or door assembly, said window or door assembly comprising a leaf moveable relative to a frame between closed and open positions, the security system comprising means for detecting whether the leaf is in its closed position or an open position, the security system including a first sensor for detecting whether the leaf has been moved or knocked, the method comprising arming said first sensor whilst the leaf is in an open position.
27. A method of operating a security system according to any of claims 21 to 25, the method comprising arming said first sensor whilst the leaf is in an open position.
28. A program for carrying out a method according to claim 26 or 27.
29. A method or security system according to any preceding claim, wherein said sensor is a one, two or three axis magnetometer.