EP2814011A1

EP2814011A1 - A cabinet alarm system and method

Info

Publication number: EP2814011A1
Application number: EP14250083.4A
Authority: EP
Inventors: Peter Jones
Original assignee: XTRA SENSE Ltd; Xtra-sense Ltd
Current assignee: XTRA SENSE Ltd; Xtra-sense Ltd
Priority date: 2013-06-13
Filing date: 2014-06-13
Publication date: 2014-12-17
Anticipated expiration: 2034-06-13
Also published as: GB2515090A; EP2814011B1; GB201310600D0

Abstract

A cabinet alarm is adapted to distinguish the sounds and forces of a genuine malicious attack on a cabinet formal normal environmental forces and sounds to which the cabinet is routinely subjected. The alarm comprises sensors to detect these noises, forces, temperatures, and rate of temperature change. Specific sensors detect noise transmitted through different pathways are indicative of specific types of attack. These specific sensors are attached to specific parts of the cabinet in specific locations that make each specific sensor particularly sensitive to a particular type of noise. Certain sensors are arranged to detect forces and change in forces between the cabinet and a base which supports the cabinet. Temperature sensors detect the temperature of the air inside the air cabinet and rate of change of air inside the cabinet. Certain combinations of physical events in a particular order are indicative of a genuine malicious attack.

Description

Field of the Invention

This invention relates generally to cabinet alarm systems and methods. More particularly this invention relates to security alarm systems and methods whereby an alert is provided only if the cabinet is subject to attack.

Background

Ticket and other vending machines are placed at locations to enable automated customer transactions and they are increasingly appearing for example at bus, tram and train stations, car parks, shopping centres and high streets.
As these machines are designed to enable automated transactions, they are typically provided at locations which may not be supervised or at least not supervised all of the time. As a consequence, machines are vulnerable to attack and vandalism, and there is a requirement to provide electronic alarms to detect inappropriate and damaging behavior which risks the loss of the machine contents (such as money or stock) and non-availability for use as well as expensive repairs to the cabinets or even complete loss due to the entire removal of the cabinets.
The nature of attacks on such machines can be divided in to the different Types of attack as follows.
Type 1 - Low impact frustration attacks where ingress is not the objective, and no damage is caused to the cabinet.
Type 2 - Vandalism where physical damaged is caused to the cabinet.
Type 3 - Concerted attempts to gain access and rob the contents.
Type 3 attacks will include:

a) Use of an Oxy-acetylene or Plasma torch welding apparatus to cut holes.
b) Use of an Angle Grinder or mechanical cutter, either electrical or petrol driven, to cut holes.
c) Use of a Sledge Hammer or Lump Hammer and 'wrecking bar' lever to attempt to open the door.
d) Use of a vehicle or similar means to ram the machine or pull it off its mountings.

It is desirable to monitor machines to detect the occurrence of an attack and to differentiate between different types of attack. For example, a Type 1 low impact frustration attack may require one type of action; whereas a Type 2 vandalism or Type 3 attempted access attack would need different responses to be initiated.
The cabinets associated with vending and ticket machines are noticeably thinner and more flexible than a standard safe. Furthermore these cabinets are located in public areas and exposed to potentially extreme weather conditions.
One issue when monitoring a cabinet is determining when an event is a genuine attack rather than something created by a normal environmental condition, and to identify the action required by the nature of the event. This also has to be done in noisy and busy environments, such as might be found on the platform of a railway station, where the alarm is to be fitted to a Ticket vending machine.

Prior Art

Security devices and methods which could be applicable to cabinets exist. A few relevant examples are:

Chinese Utility Model CN-U-201695861 for a Burglar Alarm for Safes by Zongshu,
Chinese Patent CN-Y-201297091 for an Electronic Alarm Device for a Safe, by Jiayan et al.,
Japanese Patent Application JP-A-2003041858 for a Safe with IT Function by Harada,
UK Patent Application GB-A-2306035 for a Differential Weight Security System by Williams and Jones,
UK Patent GB-B-2360119 for Sensor Systems by Williams, Jones, and Hutcheson,
UK Patent Application GB-A-2365187 for a Piezo-electric Sensor and Alarm System by Williams and Jones,
UK Patent Application GB-A-2279791 for a Motion Detecting System by Appleby,
UK Patent GB-B-2466721 for a Security System by Jones,
UK Patent Application GB-A-2264378 for a Frangible Sensor for a Secure Enclosure by Morgan,
EP Patent Application EP-A2-1981010 for a Method of Detecting Lock Bumping by Smith,
FR Patent Application FR-A1-2687240 for Sispositif de protection detectant la solicitation du mecanisme d'une fermeture et generant un signal d'information, d'aleert ou d'alarme,
FR Patent Application FR-A1-19871106 for Improvements to Devices Known as Alarm Devices, for Countering Unauthorised Intrusion into Buildings, by Milly,
US Patent Application US-A-4772874 for a Keyboard Apparatus by Hasegawa,
US Patent Application US-A1-2005/0264413 for a Dual Technology Glass Breakage Detector by Eskildsen, and
US Patent Application US-A-4383250 for a System for Intrusion Detection by Galvin

Summary of the Invention

The approach of the current invention to distinguish a genuine attack from something created by a normal environmental condition is to use at least two separate technologies, generating separate responses to an attack, to raise the confidence level of a genuine event to a point where it needs to be acted upon. The present invention takes advantage of existing technology and combines it together in a novel and inventive way with other signal processing methods to detect attacks on cabinets such as ticket machines and vending machines.
In this specification 'acoustic noise' means noise travelling through air. An acoustic noise sensor is in contact with air and senses that noise in that air through that contact with that air.
In this specification 'conducted noise' means noise travelling through the structure of a cabinet. A conducted noise sensor is in contact with the cabinet and senses that noise in the structure of the cabinet through that contact with the cabinet.
In this specification 'distortion' means strain in the cabinet. A 'distortion sensor' detects strain in the cabinet. A force applied to the cabinet causes strain in the cabinet. The distortion sensor senses this force by detecting the strain this force causes.
In this specification a thermal rate sensor is a timer combined with a thermometer sensitive to the temperature of air nearby the thermometer. The thermal rate sensor detects the time rate of change of the air temperature.
Preferably a thermal rate sensor comprises a thermometer located inside the cabinet to detect the temperature of air inside the cabinet.
According to a first aspect of the present invention there is an alert device arranged to fit to a cabinet, the alarm comprising: a timer; a first, a second and a third sensor, wherein each sensor is adapted to sense a different physical event so as to provide respective first, second and third inputs; and a means to trigger an alert in the successive events of: the first and the second sensed inputs exceeding respective first and second input thresholds during a first time period; and the third sensed input exceeding a third input threshold within or after a predetermined time interval subsequent to said first time period.
Each perpetrator who attacks a cabinet may use their method and tools to gain access to the cabinet interior. Each method has steps of attack. These steps may occur simultaneously, but often the steps of attack must be carried out in a specific order. Each step may use a unique tool. The alert alarm employs three types of sensor. Each sensor is sensitive to a sound, or vibration, or distortion, or a temperature change, an optical cue, an odour, and so on that corresponds to a specific physical event. The alert alarm has a means to trigger the alarm when the specific physical events occur in a specific sequence. The alarm is triggered only if the events occur within or after predetermined time intervals of each other. The sequence and timing of the physical events is indicative of the type of attack the perpetrator is using. Hence the alert alarm can detect an provide an alarm for many specific types of attack.
Preferably the first sensor is an acoustic sensor that detects an acoustic noise and the third sensor is a conducted noise sensor that detects noise transferred from a noise generating device to a cabinet by direct contact between the noise generating device and the cabinet. A perpetrator may attack the cabinet with grinder or mechanical cutter. First the grinder or cutter is turned on and it makes a loud whining acoustic noise. Typically the grinder is then applied to a cabinet wall within a time period of a half second to two seconds. This produces a conducted noise because the grinder vibrates the wall as its cutting blade starts to cut through.
Preferably the first sensor is an acoustic sensor that detects an acoustic noise and the third sensor is a thermal sensor that detects temperature. A typical cutting torch attack begins with the cutting torch being ignited. A pop followed by a hiss sound occurs when the torch is ignited. After igniting the torch the perpetrator cuts through the cabinet wall with the torch flame. As soon as the flame penetrates into the interior of the cabinet the noise level of the cutting flame is amplified significantly and the temperature inside the cabinet rises rapidly. The alert alarm can distinguish a cutting torch attack from background noises, normal daily temperature changes and so on because of its sensitivity to the physical event sequence and timing associated with this type of attack.
An acoustic sensor is arranged to hear sound in the air inside the cabinet. These internal sensors are hard to tamper with. The hiss of a sound of torch when it is started is more difficult to detect reliably than the sound when the flame penetrates into the cabinet. The cabinet is an enclosed space so the flame sound inside is very loud. Preferably the acoustic sensor is located inside the cabinet so as to hear sound in the air inside the cabinet.
Preferably the thermal sensor includes a means to measure the time rate of change of temperature. Torch attacks are associated with temperature rise of the air inside the cabinet that occurs much faster than the daily fluctuations of temperature due to sunrise, sunset, and weather events.
Preferably the first sensor is an acoustic sensor that detects acoustic noise; the second sensor is a conducted noise sensor that detects a noise transferred from a noise generating device to a cabinet by direct contact between the noise generating device and the cabinet; and the third sensor is a distortion sensor that detects strain changes in the structures of the cabinet due an application of force. A perpetrator may attempt to lever open the cabinet door by first hammering a lever into some part of the door to gain purchase. The hammer blow or blows to the lever will generate both characteristic acoustic and conducted noise in the cabinet. Typically a half a second up to ten seconds later the perpetrator will apply force to thelever to try and open the door, which will create a distortion of the cabinet and door. Alternatively, a perpetrator may attack the cabinet with grinder. First the grinder is turned on and it makes a loud whining acoustic noise. The grinder is then applied to a cabinet wall producing a conducted noise when the grinder vibrates the wall. The perpetrator then applies an impact to the weakened cabinet to break to break it open. The impact produces a deflection or strain in a mounting means that attaches the cabinet to a base.
Preferably the alert device comprises a processor to interpret the inputs from the first, second, and third sensors. A processor may be a programmable device. Thus if a perpetrator manages to break into a cabinet once, the sequence of events can be programmed into the processor as the attack is taking place. The processor can be programmed to trigger the alarm the next time a perpetrator tries an attack indicated by the same physical events sensed in the same sequence and within or after the same time intervals of each other. For the purpose of recording and timing the sequence of events of an attack preferably the alarm comprises additionally an acoustic sensor, further comprising a sound recording device arranged to record acoustic noise during the events which trigger the alarm.
Advantageously by monitoring the events in this fashion the alarm is only provided and the acoustic noise is only recorded in the event of a malicious attack designed to damage or gain entry to the cabinet.Preferably the alert device comprises a timing means with recording means to record signals from the sensors. Preferably the timing means is preset or is settable to record the signals for up to a minute from the start of a physical event. Anyone trying to gain access to the cabinet will create significant damage and accompanying recordable events in a minute. More preferably the time range is half to 20 seconds. A grinder or a cutting torch can cut into a cabinet in 2 to 20 seconds and by limiting the time interval less memory storage is needed to record the sensor signals.
For example preferably the alert device comprises a processor to interpret the inputs from the first, second and third sensors when (i) the acoustic noise sensor and the conducted noise sensor provide first and second inputs exceeding the first and second input thresholds respectively in the first time period; and after the predetermined time interval; (ii) the distortion sensor provides a third input exceeding the third input threshold; and also to trigger the alert in the event that: (iii) the conducted noise sensor provides a second input exceeding the second threshold in the first time period; and after the predetermined time interval, (iv) the distortion sensor provides a third input that exceeding the third input threshold; and also to trigger the alert in the event that: (v) the acoustic noise sensor provides a first input exceeding the first threshold in the first time period; and after the predetermined time interval, (vi) the distortion sensor provides a third input exceeding the third input threshold. Preferably the first input threshold of event (i) is different than the first input threshold of event (v). Preferably the second input threshold of event (i) is different than the second input threshold of event (iii). Preferably the third input thresholds of events (ii), (iv), and (vi) are all different.
However in certain cases the acoustic noise thresholds are the same, the conductive noise thresholds are the same, and particular force thresholds are the same. Advantageously this means that the cabinet alarm can be customized to trigger the alert upon an attack by a particular type of tool or combination of tools.
Preferably the first sensor is an acoustic noise sensor that detects acoustic noise in the frequency range produced by a rotary grinder or cutter, and acoustic noise in the frequency range produced by a cutting torch, and acoustic noise produced by metal on metal impact and noise in the air inside the cabinet.
Preferably the second sensor is a conducted noise sensor that detects conducted noise transferred from a noise generating device to the cabinet by direct contact between the noise generating device and the cabinet. Preferably it is detected by frequency range of conducted noise due to metal on metal impact and produced by a rotary grinder and cutter.
Preferably the cabinet alarm provides an alert in response to the occurrence of an attack event which causes major distortion of the structure of the cabinet without the generation of significant noise.
Preferably the first sensor is a distortion sensor that detects a force input in conjunction with time counted by the timer, and the events are:

(i) time rate of change of force input exceeding respective a first time rate of change of force threshold during the first time period; and within the predetermined time interval,
(ii) the force exceeding a fourth force threshold.

A typical attack that would be detected by these events is for example when perpetrator wraps a chain around the cabinet or attaches the chain to the cabinet. The perpetrator attaches the chain to a vehicle or a winch an pulls the cabinet away from its connection to the base. When the vehicle is driven away from the cabinet the chain reaches its limit and suddenly jerks the cabinet. A very high rate of change of the force applied to the cabinet to the cabinet with respect to time occurs. Sometimes the cabinet is jerked repeatedly to dislodge it from the base. Hence this type of attack can be detected from one or more rapid changes in force to weaken the attachment of the cabinet to the base followed by a large force to dislodge the cabinet. The repeated jerks give an early warning of the beginning of an attack.
Preferably once the alert is provided it continues while all sensed inputs exceed their respective input thresholds. Hence if the attack is stopped or is completed the alert is no longer provided and does not disturb people or continue to send a signal to a monitoring center that an attack is in progress. Alternatively the trigger means can be arranged to continue to provide the alert once all the physical inputs have occurred within a preselected sequence and within or after a preselected interval of each other. Hence even if the perpetrator stops or completes the attack, the alert continues to be sounded, flashed, or signaled to a monitoring center or to people in the vicinity of the cabinet. The alert may frighten the perpetrator away.
Preferably the means to provide an alert is suitable for connection to a wireless or a hardwired transmitter.
Preferably any or all the acoustic noise thresholds, the conductive noise thresholds, and the force thresholds can all be set by a user either before the alarm is installed in the cabinet or after the alarm is installed in the cabinet or both before and after by a local user or a remote user.
Advantageously the cabinet alarm is adapted to provide no alert when a cabinet is subject to routine noise and handling.
Preferably the alarm only provides an alert when a particular sequence of events occurs indicative of an attack on the cabinet.
Preferably once the alert is provided it continues until the events that initiated the alarm stop or an acknowledgement of the alert is provided back to the cabinet alarm or for a predetermined time after the alert is first provided. Preferably there is a means for the user to set the predetermined time.
In order that the present invention may be well understood, it is further explained, by way of examples, by the following description, to be read in conjunction with the appended drawings, in which:

Brief Description of the Figures

Figure 1 is a cabinet comprising a door that swings on hinges.
Figure 2 is a time trace of noise detected by an acoustic noise sensor and a conductive noise sensor before and during an attack on a cabinet by a mechanical grinder or mechanical cutter.
Figure 3 is a time trace of noise detected by an acoustic noise sensor and temperature of the air inside a cabinet before and during an attack on the cabinet by a hot gas or plasma cutting torch.
Figure 4 is a time trace of force detected by a distortion sensor and noise detected by a noise sensor before and during an attack with a lever.

Integers in Figures

10: cabinet
15: cabinet door
16: cabinet door hinge
20: base
31, 32, 33: cabinet supports
40: space between cabinet and base
50: microphone
60: temperature sensor
80: distortion sensor

Detailed Description of Preferred Embodiments of the Invention

Figure 1 illustrates a cabinet 10 comprising a door 15 that swings on hinges 16.
The cabinet 70 is supported above, and spaced apart from, a base 20 by four supports 31, 32, 33, and 34 (not shown). Due to the supports holding the cabinet above the base there is a gap, or spacing, 40 between the bottom of the cabinet and the base. The gap allows the cabinet to move on the supports if an external force is applied to the cabinet without the cabinet contacting the base.
There is a microphone 50 inside the cabinet to detect noise that travels through the air inside the cabinet before reaching the microphone. The microphone is an acoustic noise sensor.
There is a temperature sensor 60 inside the cabinet to detect the temperature of the air inside the cabinet. The temperature sensor 60 is combined with a clock (not shown) to create a temperature rate of change sensor to detect the time rate of change of air temperature inside the cabinet.
There is a conducted noise sensor 70 fixed to the cabinet.
There is a distortion sensor 80 fixed to the cabinet which distortion sensor detects distortion of the base of the cabinet due to a force applied to the exterior of the cabinet.
The supports 31, 32, 33, and 34, and gap 40 give freedom for the base to distort under an applied force.
The present invention combines noise detection, force detection, and heat detection technologies. By identifying the signal characteristics for the acoustic noise and /or the conducted noise and structural deformation generated by different types of attack on the cabinet, some, or all of these signals may be interpreted by a control microprocessor to determine the type of attack.
For example, if a wrecking bar is hammered in to the door opening to provide purchase for levering the cabinet door open, there will be characteristic acoustic signals and very large short duration conducted noise signals from the hammer blows followed by a deformation of the structure as levering is commenced. A refinement of this process is to count the number of hammer blows such that a minimum number is required to be registered before the alarm is triggered by the subsequent levering.
In the case of attacks by hot gas and angle grinder / cutters, it is typical for the cutting apparatus to be started and run for a few seconds prior to its being introduced to the cabinet to be cut and, naturally enough, for this noise to continue during the cutting process.
In the case of the angle-grinder / cutter, this will generate a large conducted noise level as soon as the cutting blade is touched on to the cabinet and if this is preceded or accompanied by a suitable acoustic noise then a serious attack is suspected. A further third sensor detecting a third physical event provides further evidence that an attack is occurring.
Figure 2 illustrates a typical time trace of noise detected by the acoustic noise sensor 50 and the conducted noise sensor 70 before and during an attack by a grinder. The time trace is a plot of the acoustic noise signal produced by the acoustic noise sensor 50 and on the same graph a plot of the conducted noise signal produced by the conducted noise sensor 70.
Almost always just before a perpetrator of an attack on a cabinet actually attacks a cabinet with a grinder or power cutter, they switch the device on. Grinders usually comprise a rotary cutting blade driven by a loud series electric motor or a loud compressed air motor. The loud noise is transmitted through the air inside and outside the cabinet and it is received and detected by the acoustic noise sensor. Preferably the acoustic noise sensor is fixed inside the cabinet. This location prevents the perpetrator from covering the acoustic noise sensor with a device to muffle the noise.
Figure 2 shows the rise in the time trace of noise detected by the acoustic noise sensor when the grinder is switched on. The level of noise produced by grinder rises above the acoustic noise threshold as illustrated.
Almost always just after the perpetrator of an attack on a cabinet turns on a grinder, they begin to cut through the cabinet by bringing the cutting blade into contact with the cabinet. The cutting blade imparts vibrations to the cabinet which is transmitted through the walls of the cabinet directly from the grinder to the conductive noise sensor which detects the conducted noise.
As illustrated in Figure 2 the conducted noise imparted to the cabinet by the grinder is above the conducted noise threshold after the grinder contacts the cabinet. Thus the conducted noise rises above the conducted noise threshold within a very short time after the acoustic noise rises above the acoustic noise threshold. This very short time is usually between a fraction of second and several seconds. Most often it is between half a second and two seconds.
When noise is detected by the acoustic noise sensor above the acoustic noise threshold a very short time before the conducted noise sensor detects noise above the conducted noise threshold, then there is a very high likelihood that the cabinet is being attacked by a perpetrator with a grinder. So when this series of events occurs then the cabinet alarm provides an alert of the attack.
In the case of a hot gas cutter, the acoustic noise detected prior to detecting a rapid rise in the air temperature inside the cabinet when the cutting flame penetrates the cabinet skin can be used as indication of a serious attack. The level of acoustic noise inside the cabinet will also amplify significantly when the cutting flame penetrates the cabinet skin, offering an alternative event forming part of a serious attack. A third sensor that can detect a third physical event can provide a higher level of confidence that an attack has occurred.
Figure 3 is a time trace of noise detected by an acoustic noise sensor and temperature of the air inside a cabinet before and during an attack on the cabinet by a hot gas cutting torch.
Almost always, just before a cutting torch cuts through a cabinet, the air inside the cabinet is relatively cool and quiet.
A cutting torch makes a whistling or hissing sound. Until the flame cuts through the cabinet, the sound of the cutting torch may be below the acoustic noise threshold for the cutting torch. However, as the flame cuts into the interior of the cabinet, the whistling or hissing sound of the torch is amplified inside the cabinet and is detected by the acoustic noise sensor 50 and exceeds the acoustic noise threshold.
Until the flame cuts through the cabinet the air inside the cabinet is relatively cool. Because the air inside the cabinet is in an enclosed space, immediately after the torch flame cuts through the cabinet to the interior the temperature of the air begins to rise quickly. Advantageously the rate of temperature rise of this air is much higher when it is due to a torch flame in the interior of the cabinet than sunlight shining on the outside of the cabinet. Therefore a time trace of the temperature detected by the temperature sensor 60 inside the cabinet that rises faster than the temperature rise rate threshold is an indicator that a flame of a cutting torch has cut into the cabinet. This is illustrated in Figure 3 by the time trace of the temperature of the air detected by the temperature sensor 60 inside the cabinet.
When the cabinet alarm detects acoustic noise and temperature changes over time as illustrated in Figure 3, there is a high probability that a perpetrator has attacked the cabinet with a hot gas cutting torch. That is the time series of events where: first, the temperature inside the cabinet is near constant or only gradually changing with the weather or change from night to day, and the level of noise inside the cabinet is below the acoustic noise threshold for a cutting torch flame, then second, the level of noise inside the cabinet rises suddenly above the acoustic noise threshold for a cutting torch flame and also the rate of temperature rise in the cabinet is above the temperature rise rate threshold for a cutting torch flame.
An alternative form of attack, which may not involve significant levels of noise is to attempt to remove the cabinet from its mountings by ramming it or pulling it off with powerful machinery. Ticket and other vending machine cabinets will be bolted down using a number of floor bolts, usually one in each corner 31, 32, 33, and 34. Any attempt to forcibly remove the unit by ramming it or tying a strap or chain round it and pulling it with a vehicle or other device, will cause significant deformation of the cabinet. This will be detected as strain by the distortion sensor 80. Identifying suitable monitoring points and setting appropriate signal level thresholds allows genuine attacks to be distinguished from environmental events, such as strong winds. The sensitivity of detection of this deformation is enhanced when the cabinet is supported only by the bolts 31, 32, 33 and 34. A gap 40 of approximately 2mm between the floor of the cabinet and its pedestal or floor mounting is ideal so that all of the weight of the cabinet is distributed between the bolts 31, 32, 33 and 34.
By providing different outputs, the cabinet alarm can identify the likely nature of an attack to initiate suitable responses.
A further improvement of the cabinet alarm is the recording of acoustic information. A rolling 30 seconds of audio on a first in, first out basis and then freeze that recording if a major alarm is generated for latter retrieval or sending as a file by the internet or mobile networks.
The invention has been described by way of examples only. The invention is further made clear and further explained in the appended claims. Substitution of substantially equivalent features to those claimed may be made to without departing from the scope of the claims.

Claims

An alert alarm arranged to fit to a cabinet, the alarm comprising:
a timer;

a first, a second and a third sensor, wherein each sensor is adapted to sense a different physical event so as to provide respective first, second and third inputs;

and a means to trigger an alert in the successive events of: the first and the second sensed inputs exceeding respective first and second input thresholds during a first time period; and the third sensed input exceeding a third input threshold after a predetermined time interval subsequent to said first time period.
An alert alarm arranged to fit to a cabinet, the alarm comprising:
a timer;

a first, a second and a third sensor, wherein each sensor is adapted to sense a different physical event so as to provide respective first, second and third inputs;

and a means to trigger an alert in the successive events of: the first and the second sensed inputs exceeding respective first and second input thresholds during a first time period; and the third sensed input exceeding a third input threshold within a predetermined time subsequent to the end of said first time period.
An alarm according to claim 1 or 2 wherein the first sensor is an acoustic sensor to hear sound in air and the third sensor detects noise transferred from a noise generating device to a cabinet by direct contact between the noise generating device and the cabinet.
An alarm according to claim 1 or 2 wherein the first sensor is an acoustic sensor to hear sound in air and the third sensor is a thermal sensor that detects temperature of the air in the cabinet.
An alarm according to claim 4 wherein the thermal sensor includes a means to measure the rate of change of temperature with respect to time.
An alarm according to claim 1 or 2 wherein the first sensor is an acoustic noise sensor to hear sound in air; the second sensor detects a noise transferred from a noise generating device to a cabinet by direct contact between the noise generating device and the cabinet; and the third sensor detects strain changes in the structures of the cabinet.
An alarm according to claims 3 to 6 wherein the acoustic noise sensor is arranged to hear sound inside the cabinet.
An alarm according to claim 1 or any preceding claim as dependent on claim 1 wherein the predetermined time interval is between one half second and two seconds.
An alarm according to claim 2 or any preceding claim as dependent on claim 2 wherein the predetermined time is between a half and ten seconds.
An alarm according to any preceding claim in which once the alert is provided it continues while all sensed inputs exceed their respective input thresholds.
An alarm according to any proceeding claim where the means to provide an alert is suitable for connection to a wireless or a hardwired transmitter.
An alarm according to any preceding claim wherein the alarm comprises an acoustic sensor, further comprising a sound recording device arranged to record acoustic noise during the events which trigger the alarm.
An alarm according to claim 12 comprising a timing device to record signals from all the signals for at least 30 seconds after the first physical event is detected.
A cabinet including an alarm according to any preceding claim.