GB2419449A

GB2419449A - Alarm System For Electrical Or Electronic Equipment

Info

Publication number: GB2419449A
Application number: GB0423439A
Authority: GB
Inventors: David Savage
Original assignee: HOTAV Ltd
Current assignee: HOTAV Ltd
Priority date: 2004-10-21
Filing date: 2004-10-21
Publication date: 2006-04-26
Also published as: GB0423439D0

Abstract

The invention provides an alarm system for electrical or electronic equipment, wherein said alarm system is responsive to disconnection of said equipment from an external power source and sets itself to an alarm mode in response to said equipment being disconnected from said external power source, said alarm system having a plurality of authorised modes which override said alarm mode, said plurality of modes including a first authorised mode corresponding to a first level of authority and a second authorised mode corresponding to a second level of authority. The alarm system may comprise a security box 2 attached to electrical / electronic equipment 1 using adhesive, for instance. The alarm system may comprise two cable parts 3b and 3c connected together through an aperture in the security box 2. The alarm system may be connected between the external power inlet 5 of the equipment and an external power outlet 4. The alarm system may include a motion sensor.

Description

24 1 9449 Alarm system for Electrical or Electronic Equipment

Field of the Invention

The present invention relates to an alarm system for electrical or electronic equipment, such as image projection apparatus.

Background of the Invention

Electrical or electronic equipment such as image projection apparatus is of high value and is occasionally the subject of theft.

Motion sensitive alarm systems incorporating a motion sensor to protect electrical or electronic equipment from thievery are known. Some of these alarms are self-setting alarms which set automatically in an alarm mode when no external power is applied to the equipment. In that alarm mode, the alarm is activated when the motion sensor senses motion above a predetermined threshold.

US patents 4284983 and 5838225 describe systems in which if authorized movement of the electronic equipment is desired, a key is operated by authorized personnel to disarm the alarm mode and mute the alarm.

It is an object of the invention to provide an improved alarm system for electrical or electronic equipment.

Summary of the Invention

In accordance with one aspect of the present invention, there is provided an alarm system for electrical or electronic equipment, wherein said alarm system is responsive to disconnection of said equipment from an external power source and sets itself to an alarm mode in response to said equipment being disconnected from said external power source, said alarm system having a plurality of authorised modes which override said alarm mode, said plurality of modes including: a first authorised mode corresponding to a first level of authority; and a second authorised mode corresponding to a second level of authority.

The invention provides at least two different modes depending on the level of authority used to override the alarm mode when the equipment is disconnected from the external power and needs transportation by authorised personnel.

In accordance with a second aspect of the present invention, there is provided an alarm system having a motion sensor for electrical or electronic equipment, wherein said alarm system is responsive to disconnection of said equipment from an external power source and sets itself to an alarm mode in response to said equipment being disconnected from said external power source, said alarm system having a plurality of alarm modes in which an alarm is capable of being activated, wherein said plurality of alarm modes include: a first alarm mode, in which said alarm is capable of being deactivated in response to a first deactivation procedure; and a second alarm mode in which said alarm is capable of being deactivated in response to a second deactivation procedure, wherein at least one of said first and second deactivation procedure is selectively enabled in dependence on the current alarm mode.

By providing at least one different deactivation procedure in the respective alarm modes, different alarm modes can be selected in different circumstances in which an alarm may be set.

Further features and advantages of the invention will become apparent from the following description of preferred embodiments of the invention, given by way of example only, which is made with reference to the accompanying drawings.

Brief Description of the Drawings

Figure I is a schematic perspective view illustrating an alarm system attached to the audio visual equipment in accordance with an embodiment of the present invention.

Figures 2, 3, 4 and 5 are flow diagrams illustrating the operation cycle of the alarm system according to an embodiment of the present invention.

Figure 6 shows a block diagram of the alarm system circuit according to an embodiment of the present invention. s

Detailed Description of the Invention

Figure 1 is a schematic perspective view illustrating an alarm system attached to audio visual equipment in accordance with an embodiment of the present invention. The alarm system is, in this embodiment, a retro fit in the form of a security box 2 having two cable parts 3b and 3c connected together through an aperture in the security box 2. The plug of cable part 3c fits into the socket S of the audio visual equipment 1 and cable part 3b is connected via a cable part 3a to the external power source 4. The box can be attached to the audio visual equipment via a suitable fixing method, such as mechanical IS attachment or attachment by means of an adhesive. Preferably, the fixing method is by means of a structural adhesive, most preferably a methyl methacrylate composition.

The audio visual equipment is provided with a self-setting motion sensitive alarm system which can monitor the external power status of the equipment (i.e. on or off). The alarm system is in a normal usage mode, i. e. is reset and mutes, when the equipment is connected to the external power irrespective of whether movement of the equipment is sensed. The alarm system sets itself to a full alarm mode in response to the equipment being disconnected from the external power source and actuates the motion sensor.

To allow legitimate operations such as site to site transportation, room to room transportation or storage when there is no external power applied and to reduce the risk of theft during these operations, the invention provides three types of keys, i.e. a user key, a service key and a reprogramming key.

The user key which can be used for example by authorised personnel for transportation of audio visual equipment between rooms, sets a first authorised mode (i.e. an authorised user transportation mode) corresponding to a first level of authority which overrides the full alarm mode. While the user key is in the equipment irrespective of motion being sensed or not, the alarm emits a reminder sound or warning alert such as a beep say every 10 seconds to remind the user to remove the user key once the transportation is completed.

The service key, which can be used for example by authorised personnel from a service company for transportation of the audio-visual equipment between sites or for maintenance, sets a second authorised mode (i.e. an authorised service mode) corresponding to a second level of authority which also overrides the full alarm mode. Once inserted and removed the service key mutes and switches off the alarm completely allowing movement of the equipment without the service key in it.

According to another feature of the invention, when the user key is removed and with no power applied, the alarm system automatically sets from the first authorised mode (i.e. the authorised user transportation mode) to a different alarm mode (i.e. a storage alarm mode) after a period of say 10 minutes corresponding to the equipment being stored in a cupboard for example. In this mode, the alarm will only sound when motion is detected by the motion sensor.

If no key has been detected in the equipment and the equipment is moved when external power is off (i.e. in a "grab and run" scenario), the alarm sounds. In this case, when initial movement has been detected by the sensor, the alarm system could be arranged to check for continued movement after a specified period of time so as to distinguish between illegitimate and accidental movement; if no further movement is detected the alarm sound switches off; alternatively, it continues and can even increase in volume. It could also beep quietly for say 10 seconds before emitting an alarm sound (90-100 dB). During those 10 seconds or when the alarm sounds, the reapplication of the external power deactivates the alarm. The motion sensor can be set on a sensitive mode when no key is inserted and on a less sensitive mode when a key is inserted.

In these different alarm modes set by the insertion of a user or service key, the reapplication of the external power to the equipment restores normal usage mode (alarm off. If the external power is then removed, the full alarm mode is set again. Also, according to an embodiment of the invention, in the full alarm mode or storage alarm mode wherein an alarm sound is activated when motion is sensed, the alarm sound can be deactivated in response to a deactivation procedure being selectively enabled in dependence on the current alarm mode (i.e. full alarm mode or storage alarm mode). These deactivation procedures will be described in Figures 2, 3, 4 and 5.

Seven user keys and one service key for example could be available for multiple users and in the same way, several projectors or other units of equipment could be operated by a handful of keys. These keys could be electronic coded keys. The alarm would leave manufacture un-encoded but with coded user and service keys. An explanation on how the data on the key get accessed by the alarm system and how the alarm system distinguishes user keys, or service keys will be provided later.

The invention also proposes a provision for lost keys to be replaced using a re-programming key which is inserted in the equipment to encode the alarm so that the lost keys cannot be reused. The re-programming key which can be supplied by the service company unlocks the alarm, downloads a unique code into the alarm and finally re-activates the alarm in a reprogramming mode.

In this re-programming mode, the service key is first encoded and one or several user key(s) maybe be coded with a maximum window of say 32 seconds between coding of each key. Once used, the re-programming key becomes a user key.

Figures 2, 3, 4 and 5 are flow diagrams illustrating the operation cycles of the alarm system according an embodiment of the present invention.

Referring to Figure 2 and presuming the equipment is connected to the external power, the alarm system is off irrespective of whether movement of the device is sensed, step S1. In step S2, the removal of the external power is monitored.

When the external power is off, the alarm system is set to the full alarm mode, step 3, and the motion sensor is actuated. Next, step S4, it is determined whether a key is inserted in the equipment. If a key is inserted, it is then determined whether it is a correct service key, step S5. If it is the case, the system switches to the authorised service mode, step S6, which is described in further detail in Figure 4, wherein the alarm is switched offcompletely. This for example corresponds to the scenario where authorised personnel from the service company uses a service key for transportation of the equipment between sites or for maintenance. If it is not the case, it is determined whether it is a correct user key that is inserted, step S7. If yes, the system switches to the authorised user transportation mode, step S8, which is described in further detail in Figure 3. If the key inserted is neither a correct service key nor a correct user key, the alarm emits a key reject sound, step S9, notifying the user of his error and the cycle is repeated again starting at step S2.

Considering again step S4, in case that no key was inserted, it is then determined if motion is detected by the motion sensor, step S10. If not, the cycle is repeated again starting at step S2. If motion is sensed, an alarm sound is activated, step S11. The alarm sound is deactivated if a deactivation procedure is enabled. This deactivation procedure consists in monitoring if the external power is reapplied, step S 12, and then monitoring for a length of time, step S 13, while the external power is still on before deactivating the alarm, step S14 and going back to step S2. Alternatively in the case of a "grab and run" scenario, if the external power is not reapplied, step S12, the alarm continues to sound, step S l l and again reapplication of the external power is monitored, step S 12.

Figure 3 describes the operation of the alarm when the system is in the authorised user transportation mode, step S8, which corresponds for example to the scenario where authorised personnel transport the equipment from room to room using a user key. In that case, the alarm emits a reminder sound, i.e. a beep, step S 15 to remind the user to remove the user key such as determined in step S17. The length of this warning sound is determined by the length of the timeout of step S16. When the key is removed, the reminder sound stops and the system is set in the storage alarm mode, step S 18. In this mode, corresponding for example to the equipment being stored after having being transported with a user key, the alarm will be activated, step S21, only if the external power has not been reapplied, step Sl9, and if motion is detected, step S20, but the alarm is mute when no motion is detected. The alarm sound is deactivated if a deactivation procedure is enabled, say by a user having accidentally moved the equipment in that particular mode without any key being in. This deactivation procedure consists in monitoring if the external power is reapplied, step S22, and if yes, the alarm is deactivated, step S23, and the cycle is repeated again starting at step S1. Alternatively, if not, further motion is detected, step S24, the alarm sounds until no motion is detected, thus deactivating the alarm, step S25.

Figure 4 describes the operation of the alarm when the system is in the authorised service mode, step S6. In this mode, the alarm is switched off completely and the system reverts back to the normal usage mode, step S1, when the external power is reapplied, step S26. If the external power is not reapplied at step S26, the system stays in the authorised service mode, step S6.

Figure 5 describes the operation of the alarm when the system is in the re-programming mode. This mode can be used when lost keys have to be replaced using a re-programming key. The re-programming mode is entered by inserting the re-programming key in the equipment to encode the alarm.

Starting from any mode, the re-programming key, which can be supplied by the service company, unlocks the alarm, downloads a unique code into the alarm and finally re-activates the alarm in a re-programming mode, step S27. In this re-programming mode, the identities of the previously encoded set of keys are deleted from the memory of the alarm system, and the identity of the re- programming key is stored. It is next determined if a key to be encoded, which may be either a service key or a user key, is inserted in the equipment, step S28, with a maximum window of say 32 seconds for the user to insert a key (timeout of step S33) before the system reverts back to the previous mode. If a key is inserted before the timeout lapses, the identity of the key is sent from the key to the alarm system where it is encoded in memory in the alarm system, step S29, and a sound is emitted, step S30, when the encoding process is terminated. It is then determined if the key is removed, step S31, and if yes, if the maximum number of keys than can be encoded is reached, step S32. If not, the insertion of l a new key to be encoded is monitored, step S28, with a maximum window of say 32 seconds for the user to insert a new key (timeout of step S33) before the system reverts back to the previous mode, step S34. When the maximum number of keys than can be encoded is reached, step S32, the system reverts back to the previous mode, step S34.

The alarm system main components will now be described in further detail. Figure 6 is a block diagram of the alarm system circuit according to an embodiment of the present invention which comprises an external power supply 100, a power conditioning system 101, a charging circuit 102, a battery 103, an alarm sounder 104, a processor 105, a vibration sensor 106, a key slot/reader 107 and an edge connector 108.

The external power supply 100 is connected to the power conditioning system 101 by cable parts 3a and 3b, and onwards to the audio visual equipment by cable part 3c. The external power supply 100 could operate with any suitable voltage, for example between I OOV and 240V AC (48 Hz to 62 Hz). The power conditioning system 101 includes for example a low power impedance protected transformer which provides power to some rectification diodes (components not represented) to generate a half wave rectified supply.

A pseudo constant current charging circuit 102 is used to limit the charging current over the wide input voltage range of lOOV to 240V which is reflected at a voltage of 9 to 18 volts on the secondary side of the transformer of power conditioning system 101. The circuit is preferably voltage limited via a Zener diode which, in combination with a resistor, cause the charging current to cut back from about 4 mA to a safe trickle charge of about 0.5 mA during the charging cycle of a discharged battery to a fully charged battery 103. The detection of the external power being on or off is obtained by a feed to the processor reset 105 which provides a pulse every half cycle of the voltage supply to keep the processor reset during the application of external power to the alarm system.

The battery 103 is recharged when the external power is applied to the equipment via the transformer of power conditioning system 101, so that the battery is always charged with or without power applied to the equipment. The battery is connected to OV via a link to allow testing of the unit. The alarm 104 takes its feed from the battery directly, whereas the processor circuitry is isolated from the raw supply.

The alarm sounder circuit 104 is for example based on a piezo sounder.

The alarm circuit uses switch mode power supply techniques to generate a high voltage drive for the piezo sounder.

The processor 105 captures pulses from the vibration sensor 106 and drives the alarm 104. The processor could apply an averaging algorithm to the vibration sensor signal to set a minimum level of sensitivity so as to ensure that movement is detected and to prevent spurious alarm sounding.

The vibration sensor 106 is for example a standard mechanical and hermetically sealed, mercury or non-mercury motion sensing switch. It can be arranged to detect movement only if the device power is off.

As mentioned above, the alarm system could leave manufacture un encoded but with coded user and service keys. The edge connector (Edge Con / 108) is provided to enable loading of the software in the processor and testing of the alarm system after manufacture.

The alarm system once encoded is able to distinguish which type of key is being inserted in the key slot/reader 107. The key slot/reader 107 is a three contact connector providing access to the processor 105 by inhibiting the reset of the processor when a key is inserted into the key slot/reader 107. A software delay of say 1.5 seconds is provided to allow the alarm software in the processor to prepare for data transmission from the key. The key is detected and a serial data burst is received at the processor 105 after a finite delay, the communication link being one-way. The data contains a key identity consisting of a key code, key type and issue type. The key code is a 3 byte serial number.

The key type is a single byte corresponding to the type of key being used. The issue type allows customers to be identified such that the key codes are unique to that customer. The processor 105 looks at the data to establish whether to go to the authorized service mode (if a service key is detected), to the authorized user transportation mode (if a user key is detected), to the re-programming mode (if a re-programming key is detected) or to ignore the key if an incorrect key is inserted.

The above embodiments are to be understood as illustrative examples of the invention. Further embodiments of the invention are envisaged. For example, an alarm system according to the invention could be applied to display equipment such as plasma screens, desktop computers, portable computers, video players or other electric or electronic equipment. Further, whilst the alarm system is in a described embodiment a retro fit, it can be in an alternate embodiment an integral part of the audio visual equipment. It is to be understood that any feature described in relation to any one embodiment may be used alone, or in combination with other features described, and may also be used in combination with one or more features of any other of the embodiments, or any combination of any other of the embodiments. Furthermore, equivalents I S and modifications not described above may also be employed without departing from the scope of the invention, which is defined in the accompanying claims.

Claims

Claims 1. An alarm system for electrical or electronic equipment, wherein

said alarm system is responsive to disconnection of said equipment from an external power source and sets itself to an alarm mode in response to said equipment being disconnected from said external power source, said alarm system having a plurality of authorised modes which override said alarm mode, said plurality of modes including: a first authorised mode corresponding to a first level of authority; and a second authorised mode corresponding to a second level of authority.
2. An alarm system according to claim 1, wherein in said first authorised mode said alarm system emits a warning alert, and wherein said warning alert is emitted both when motion is sensed or is not sensed.
3. An alarm system according to claim I or 2, wherein in said second authorised mode said alarm system is muted.
4. An alarm system according to claim 1, 2 or 3, wherein said first and second authorised mode are set by user authorization means.
255. An alarm system according to claim 4, wherein each of said user authorization means includes one or a plurality of coded key(s).
6. An alarm system according to any preceding claim, having encoding means to encode said alarm system.
7. An alarm system according to claim 6, wherein said encoding means is an encoding key.
8. An alarm system according to claim 4 or 5, and claim 6 or 7, wherein said encoding means becomes user authorization means once the encoding of said alarm system is completed.
9. An alarm system according to any preceding claim, wherein said alarm system includes a motion sensor, and wherein said alarm system is activated in response to motion being sensed by said motion sensor, when said alarm system is in said alarm mode.
10. An alarm system according to claim 9, wherein, when external power is reapplied when in said alarm mode, said alarm system is set to a normal usage mode in which said alarm system is not activated in response to motion being sensed by said motion sensor.
11. An alarm system according to any preceding claim, wherein said alarm system can be set in a different alarm mode.
12. An alarm system according to claims 9 or 10, and claim 11, wherein in said different alarm mode, said alarm system is activated when motion is sensed by said motion sensor, and said alarm system is subsequently deactivated when no motion is sensed by said motion sensor.
13. An alarm system having a motion sensor for electrical or electronic equipment, wherein said alarm system is responsive to disconnection of said equipment from an external power source and sets itself to an alarm mode in response to said equipment being disconnected from said external power source, said alarm system having a plurality of alarm modes in which an alarm is capable of being activated, wherein said plurality of alarm modes include: a first alarm mode, in which said alarm is capable of being deactivated in response to a first deactivation procedure; and a second alarm mode in which said alarm is capable of being deactivated in response to a second deactivation procedure, wherein at least one of said first and second deactivation procedures is selectively enabled in dependence on the current alarm mode.
14. Electrical or electronic equipment having an alarm system which is fixed to said electrical or electronic equipment by adhesive means and which connects an external power outlet to an external power inlet of said electrical or electronic equipment, said alarm system being responsive to disconnection of said external power inlet of said equipment from said external power outlet and sets itself to an alarm mode in response to said external power inlet of said equipment being disconnected from said external power outlet.