A WARNING DEVICE

Abstract: A warning device comprising two circuits for connection respectively to an AC and a DC supply. A first switch (4) in series with a triggerable switch means (8 and 9) in the first circuit. The first switch (4) is rendered non-conductive by the application of AC to the first circuit. An orientation sensing means (10) which will dependent upon its orientation trigger or fail to trigger the triggerable switching means (8 and 9). An alarm (6) which is energised when the triggerable switching means (8 and 9) is triggered and the first switch (4) is conductive. Latching means activated by triggering of the switching means (8 and 9) to maintain the alarm (6) operating irrespective of the orientation of the sensing means (10).

Description: A WARNING DEVICE This invention relates to a warning device with an associated alarm which is activated when the device is moved from a predetermined orientation. The device has a primary function as a theft deterrent and is intended to be mounted in valuable articles such as video cassette recorders, television receivers and computers, to name only a few such articles. In the following specification the general terms alarm,, auxiliary power, key switch, sensor and apparatus will be used and these terms are to be considered as having anyone of the several meanings hereinafter attributed thereto. Alarm means any hooter, bell, beeper, claxon or similar audio or visual warning either continuous or intermittent which can be electrically initiated or powered. Auxiliary power means a battery or like self-contained source of electrical energy. Key switch means a switch for making, and breaking an electrical circuit. and which is operated with or by a device OMPI which can be applied to the switch to turn it ON or OFF and can be taken away therefrom. Examples are a key of conventional form, or a magnetic card key or the like with the limitations that the device is one that can be coded, bitted, or otherwise incorporates information which can provide security for and limit operational access to apparatus protected by the alarm. Sensor means a mercury, thermal, infra-red, ultrasonic, magnetic reed, micro or other switch which will detect shock, movement, proximity or other condition of apparatus with which it is associated,, other than a predetermined condition, and which will open or close a circuit if the predetermined condition is changed. Apparatus means an article or articles which need protection from theft or unauthorised removal from a given location and includes but is not limited to a video cassette recorder, a television receiver, a computer, a sound system, an electrical organ or like electrically powered articles. For convenience the term VCR will be used herei to identify a video cassette recorder as a representative item of apparatus as it is for the protection of VCR's that the invention has been primarily devised. In the case of a VCR the warning device must allow normal handling such as bumping and other sharp movements, removal from one place to another and for movement to allow for household cleaning, all whilst connected to power. The device is adapted to be armed upon the creation of a trigger condition which is created by disconnecting the VCR from mains power. Once armed the alarm will be activated, if the VCR is moved, bumped or otherwise interferred with sufficiently to cause a sensor to be activated. Authorised movements of the VCR in the above ways must however be possible when the VCR is disconnected from the mains power supply. In order to permit this to happen there is a key switch which will over-ride the warning device. The sensor is included to ensure that' should the VCR be disconnected from the mains power supply by accident, as by a fuse failure, or power shedding, storm damage to power lines and the like, the alarm will not be activated. It is only when a subsequent sensor dectectable condition occurs, such as a movement of the VCR, that the alarm will be activated. The device also includes means to ensure the alarm will sound until a stable electrical condition is restored, that is achieved by the reconnection of the VCR to the mains power supply or by interruption of the alarm actuating power supply after a predetermined time of alarm C∑.fPi operation. In the case of an authorised person the condition can be achieved by operation of the key switch to OFF. An apparatus fitted with the device of the invention can have four conditions. In the first condition the VCR is connected to a power supply which is switched on, and the key switch is on, this allows the VCR to be moved and used as required within the limits defined by the length of the power supply cord. In the second condition the power supply is switched off at the power point and the key switch is on. under these conditions the VCR will not operate and activation of the sensor will cause the alarm to sound until the key switch is operated, the power is reconnected to the VCR or a timing device interrupts the power supply to the alarm. In the third condition the VCR is connected to power and the key switch is off allowing the VCR to be used and moved about as required within the limits defined by the length of the power supply cord. This is not a recc-inrended condition as the warning device is inoperative and if the user forgets to turn the key switch ON the VCR will not be protected. - b - In the fourth ' condition the VCR is disconnected from power and the key switch is off allowing the VCR to be moved about as required. Broadly the invention can be said to comprise a warning device comprising first and second electric circuits which are respectively adapated for connection to an AC supply and a DC supply, said first circuit including a first switch rendered respectively non-conductive or conductive by the presence or absence of said AC supply, said second circuit including an alarm device, a triggerable switch means and said first switch connected in series, said switch means being triggerable by an orientation sensing device which dependent upon whether it is in a predetermined orientation or not will respectively fail to or effect triggering of said switch means to allow conduction of current through said alarm and said switch means if said first switch is conductive, conduction of current through said switch means operating a latching circuit therefor to permit continued conduction of current through said switch means notwithstanding cessation of triggering thereof by said orientation sensing device. The invention will now be described with reference to the OMPI accompanying drawings in which:- Fig.l is. a block diagram of the warning device of the invention, Fig.2 is a circuit diagram of the device in a presently preferred form and Fig.3 is a circuit diagram of an alternate arrangement, for the device. The device has four major components namely an auxiliary DC power supply (a battery disconnectable from the device as required for replacement) indicated A in Fig.l, a manually operable switch in the power supply line from the DC power supply, indicated B in Fig.l, an electrically operated alarm, indicated C in Fig.l and a control circuit, indicated D in Fig.l. Referring now to Fig.2, the general functioning of the components is as follows. The diode 1 rectifies the negative going voltage of the 240V AC supply and this charges the capacitor 3 through the resistor 2. The storage takes place during the positive portion of the mains power cycle. This negates the positive bias applied to the base of the mains monitoring transistor 4 through the resistor 5 and the alarm 6 will not operate. The alarm 6 in this presently preferred arrangement is of the oscillating type although a DC activated alarm can be used. In the second possible condition of the device, as described above, the 240V power supply is disconnected and there is no negative bias to the transistor 4, rather a positive bias is applied to the transistor 4 via the resistor 5. However, current is unable to flow between collector and emitter of transistor 4 since the transistor 9 is OFF because of an absence of positive base bias since the resistor 11 is not connected to the positive terminal via-orientation sensing device 10 (preferably a mercury or like switch) . The resistor 13 ensures that the transistor 9 remains in the OFF condition until the orientaion sensing device 10 is ON. The AC supply can thus be switched ON and OFF without triggering the alarm 6. However, if the device, or a piece of apparatus in which it is mounted, is moved sufficiently to cause the sensing device 10 to adopt a conductive ON position there will be a supply of base current to the transistor 9 which will conduct (if possible) via the transistor 4. If movement sufficient to turn the device 10 ON occurs whilst the mains supply is still connected, thereby providing a reverse bias to the transistor 4, neither transistor 4 nor 9 will conduct . If the mains supply is not connected and the device 10 is ON the transistors 4 and 9 are both forwardly biassed and both conduct. Transistor 9 draws its collector current through the base emitter of the transistor 8, which supplies more current via its collector-emitter circuit to the base of transistor 9. This results in more current being drawn from the base of the transistor 8 and this action will continue, regardless of the condition of the orientation sensing device 10, until the transistor ' s 8 and 9 are both saturated. This sequence is freguently technically referred to as regenerative action. Current will now flow from the positive terminal 7, through the switch 12a and the alarm 6 and divide to flow through the transistors 8 and 9. The current then recombines to flow through transistor 4 to the negative terminal 7. As a result of the current flow the alarm 6 will be operated with the alarm circuit "latched" in the conductive condition. Once the latch has been activated it will remain activated until the negative bias is re-established at the base of the transistor 4 by reconnecting the. device to mains power to render the transistor 4 non-conducting. Since transistor 4 ' rt.-. O ?r - Q _ conducts the base current for the transistor 8 (via transistor 9), when the mains supply is reconnected the transistors 4, 8 and 9 cease conducting. Alternatively, the key switch 12a can be used to disconnect the DC supply. The transistor 9 will lose its forward base bias, the transistor 8 will lose its forward base bias and the alarm 6 ceases to operate. The other components of the device are the capacitor 12 which provides a low impedance path for the current of the oscillator type alarm 6, the hold down resistor 13 and the capacitor 14 which prevents false triggering when the DC voltage is applied to the circuit. In the circuit diagram of Fig.3 the AC voltage when applied activates a mains optic-coupler 15 of known type, typically of the type G.E.4N28 or Seimans 4N25 via resistors 16 arid 17. The diode 18 ensures that the peak inverse voltage rating of the diode in the optic-coupler 15 is not exceeded. When mains voltage is applied the base of the transistor 19 is held low by the optic-isolator 15. The capacitor 20 ensures that the base of transistor 19 cannot rise during the alternate half-cycles of the mains supply, when an L.E.D. in the optic-coupler 15 is not illuminated. When the transistor 19 is not conducting there is no current flow to the base of the transistor 21 and there wil "1 be no curren flow through the DC out terminals 22 and 23. When the mains supply is removed transistor 19 will draw current through resistor 24 and will become conductive and there will be a current supply to the base of the transistor 21. It is to be noted that the member 25 is in a non-conducting mode because its gate is held low by the resistor 26. If the silicon controlled rectifier is now triggered by the mercury switch 27 closing current will flow through the members 25 and 21. Capacitor 28 ensures a low impedance path for any AC component in the external circuit. Once triggered the circuit is "latched" until the DC supply is interrupted by a suitable switch, for example a key switch, or until the mains supply is re-connected to remove the supply of current to transistor 19.

Claims: THE CLAIMS : - 1. A warning device comprising first and second electric circuits which are respectively adapated for connection to an AC supply and a DC supply, said first circuit including a first switch rendered respectively non-conductive or conductive by the presence or absence of said AC supply, said second circuit including an alarm device, a triggerable switch means and said first switch connected in series, said switch means being triggerable by an orientation sensing device which dependent upon whether it is in a predetermined orientation or not will respectively fail to or effect triggering of said switch •means to allow conduction of current through said alarm and said switch means if said first switch is conductive, conduction of current through said switch means operating a latching circuit therefor to permit continued conduction of current through said switch means notwithstanding cessation of triggering thereof by said orientation sensing device. 2. A warning device as claimed in claim 1 wherein the orientation sensing device is a mercury switch. OMPI

Inventors: COLLINS RONALD ARTHUR, COLLINS, RONALD, ARTHUR
Applicants: COLLINS RONALD ARTHUR, COLLINS, RONALD, ARTHUR
Application year: 1984
Main classification: G08B13
IPC codes: G08B13