This invention relates, generally, to the detection of hydrocarbon based gases and, more particularly, to a system for detecting hydrocarbon based gases. The invention is particularly, but not necessarily exclusively, for use in an automatic teller machine (ATM).

Background to the Invention

People wishing to gain access to valuables stored in an enclosed, confined volume often make use of explosives to damage a structure defining the confined volume to an extent sufficient to be able to gain access to the volume. Examples of such structures include cabinets for automatic teller machines, safes, reinforced rooms in a building, etc.

The explosives in question are normally hydrocarbon based and emit hydrocarbon based gases. The detection of such gases may be useful in alerting authorities that an unlawful attempt to access the valuables is occurring enabling action to be taken. For the sake of brevity, the hydrocarbon based gases will be referred to below as "hydrocarbon gases".

Summary of the Invention

According to a first aspect of the invention there is provided a system for detecting hydrocarbon gases, the system including a controller; a first hydrocarbon gas sensor mountable within an enclosed structure remote from an opening of the enclosed structure; and at least one further hydrocarbon gas sensor mountable within the enclosed structure in the vicinity of the opening of the enclosed structure, the sensors being individually programmable via the controller to generate an alarm condition when at least one predetermined parameter is detected by at least one of the sensors, the at least one parameter being one of a level of hydrocarbon gases in the vicinity of at least one of the sensors and a period of time for which a predetermined level of hydrocarbon gases is present in the vicinity of at least one of the sensors.

Preferably, the system includes two sensors. The controller may be configured to be responsive to one or more of the sensors. The controller may be connectable to an alarm generating unit via a fail-safe switching arrangement. The fail-safe switching arrangement may comprise a relay associated with each sensor. Preferably, each relay is a normally closed relay so that, in the event, of a power failure or other adverse condition occurring, the relays open to generate an alarm signal.

The system may include a counter-measure circuit board in communication with the controller. Preferably, the counter-measure circuit board communicates serially with the controller. The counter-measure circuit board may include at least one actuator for actuating a counter-measure device, the counter-measure circuit board further including an energy generating unit for generating a high energy trigger signal for the at least one actuator. The counter-measure circuit board may include a switching unit for sending the trigger signal to the at least one actuator for inhibiting spurious triggering of the at least one actuator.

The controller may communicate with the counter-measure circuit board via encrypted signals.

According to a second aspect of the invention, there is provided an automatic teller machine having a housing with at least one opening being defined in the housing, the automatic teller machine including a controller arranged in the housing; a first hydrocarbon gas sensor mounted within the housing remote from the opening; and at least one further hydrocarbon gas sensor mounted within the housing in the vicinity of the opening of the enclosed structure, the sensors being individually programmable via the controller to generate an alarm condition when at least one predetermined parameter is detected by at least one of the sensors.

Brief Description of Drawings

An embodiment of the invention is now described by way of example with reference to the accompanying drawing in which :-

Fig. 1 shows a schematic block diagram of an embodiment of a system for detecting hydrocarbon gases; Fig. 2 shows a block diagram of a controller of the system of Fig. 1;

Fig. 3 shows a simplified circuit layout of a gas sensor of the system; and

Fig. 4 shows a block diagram of a counter-measure board of the system.

Detailed Description of Exemplary Embodiment In Fig. 1 , reference numeral 10 generally designates an embodiment of a system for detecting hydrocarbon gases. While the system 10 can be used to monitor any confined volume, the system 10 is intended particularly for use with automatic teller machines (ATMs). For ease of explanation, the system 10 will be described with reference to its application to ATMs.

The system 10 comprises a housing 12 housing a controller 14. The system 10 further includes a first hydrocarbon gas sensor or sensor head 16 arranged in proximity to the controller 14. A second hydrocarbon gas sensor or sensor head 18 is arranged remote from the controller 14.

It will be appreciated that an ATM has a deposit chute in which envelopes containing currency or cheques to be deposited are receivable. In addition, the ATM has a money holding tray. The housing 12 housing the controller 14 and the first gas sensor head 16 is, for example, arranged in proximity to the tray 14. The sensor head 16 is therefore operable to detect the presence of hydrocarbon gases close to the tray. Conversely, the sensor head 18 is arranged in the vicinity of an entrance opening to the deposit chute of the ATM and is spaced from the housing 12 housing the controller 14. Conveniently, the sensor head 18 is connected to the controller 14 via a connector 20.

It will be appreciated that, if desired, the sensor head 16 can be mounted within the controller 14.

The sensor heads 16 and 18 are individually programmable by the controller 14 to generate an alarm condition when a predetermined parameter is detected by at least one of the sensor heads 16, 18.

Preferably, each sensor head 16, 18 is programmable to detect a preset level of hydrocarbon gas. Each sensor head 16, 18 is programmable in increments between 0 and 100% of hydrocarbon gas level. The level of hydrocarbon gas is referred to as Ll for sensor head 16 and L2 for sensor head 18. In addition, each sensor head 16, 18 is programmable so that the level of hydrocarbon gas present at the sensor head 16, 18 must be present for a predetermined period of time known as Tl for sensor head 16 and T2 for sensor head 18.

The controller 14 has a liquid crystal display 32 (Fig. 2) for the indication of trigger levels for the sensor head 16, 18 and any setup levels and current display levels. In addition, the system 10 includes a serial port 15 in communication with the controller 14. A computer or other device can be plugged into the serial port 15 to indicate what the current settings of the controller are and also to provide an indication of a history of levels detected by the sensor heads 16 and 18 every 12 hours for a predetermined number of events, for example, the preceding 100 events. By means of the controller 14, Ll and Tl for sensor head 16 can be set at desired values and, similarly, L2 and T2 can be set at the desired values for sensor head 18. In addition, the controller is operable in an OR-type manner or an AND-type manner. In other words, if the required level of hydrocarbon gas is detected by either sensor head 16, 18 for the preset period of time, the relevant sensor head 16, 18 may cause an alarm condition to be generated (OR-type operation). Conversely, the controller 14 can be programmed so that both sensor heads 16 and 18 need to detect their required level of hydrocarbon gas for the preset period of time for each sensor head 16, 18 before an alarm condition is triggered (AND-type operation).

Each sensor head 16, 18 has a tamper indicating device, indicated schematically by a switch 22 associated with it so that, should an attempt be made to tamper with either sensor head 16, 18 for example, to attempt to remove either senor head 16, 18, an appropriate signal will be sent to the controller 14 which will cause an alarm condition to be generated.

The system 10 further includes a power supply 24 which is regulated and filtered to provide a reliable source of power for the controller 14 and the gas heads 16, 18.

The system 10 includes two relays 26, 28, one associated with each gas head 16, 18, respectively. The relays 26 and 28 are of either a normally open or normally closed configuration and designed in a fail-safe type configuration. In other words, each relay 26, 28 is always energised and will drop to a non-powered state in the event of no power being supplied to the system 10 or upon the detection of an alarm condition by either or both of the sensor heads 16 and 18, dependent on the manner in which the controller 14 has been programmed. Thus, when an alarm condition is detected, the relays 26, 28 drop to a non-powered state causing an alarm condition to be generated.

It will further be appreciated that the alarm is generated at a location remote from the ATM in which the system 10 has been installed so that preventative action can be taken by the authorities if suspicious activity occurs at the ATM. This suspicious activity will be an attempt to blow the ATM open using explosives having hydrocarbon signatures resulting from the release of hydrocarbon gases.

Referring now to Fig. 2 of the drawings, a block diagram of the controller 14 is shown in greater detail.

The controller 14 includes a microprocessor 30 to which the display 32 is connected. The sensor heads 16, 18 are connected to the microprocessor 30 via an input port 34.

An I/O control block 36 is connected to the microprocessor 30. Switches, buzzers, dipswitches, or the like (not shown), are connected to the microprocessor 30 via the I/O control block 36. As described above, the controller 14 includes a serial port 15 in communication with the microprocessor 30. This serial port 15 is an internal serial port. The controller

30 includes a second, external serial port 38 to which a counter-measure circuit board

40 (Fig. 4) is connected. The counter-measure circuit board 40 will be described in greater detail below.

The relays 26 and 28 are connected to the microprocessor 30 to generate the alarm conditions when the sensor heads 16, 18, detect an alarm condition, as described above. In addition, the controller 14 includes a third, optional relay 42. The relay 42 can be used for any desired purpose. For example, the relay 42 can be used to trigger the ATM to shutdown, for dye release, or the like. Further, it will be appreciated that instead of the relays 26, 28 and 42, the outputs could be logic outputs, voltage outputs, or the like.

Referring to Fig. 3 of the drawings, a simplified circuit board of each sensor head 16, 18 is shown. Each senor head 16, 18, includes a gas sensor 44, an adjustable power supply 46 and a power regulator 48. An enunciator in the form of a light emitting diode 50 is connected to the power regulator 48.

As described above, each sensor head 16, 18 also includes tamper detection circuitry 22. The tamper detection circuitry 22 is a resistive matrix circuit. Finally, the board includes a connector 52 via which each sensor head 16, 18 is connected to the controller 14.

In Fig. 4 of the drawings, a block diagram of the counter-measure circuit board 40 is shown. The counter-measure circuit board 40 includes a microprocessor 54 having a serial port 56 which communicates with the serial port 38 of the controller 14. The counter-measure circuit board further includes an external input port 58. Desired inputs are connected to the microprocessor 54 via the input port 58. For example, the counter-measure circuit board 40 can be connected to a door of the ATM or an alarm to prevent the counter-measure circuit board being triggered as a safety measure. For example, when the door of the ATM is open, the counter-measure circuit board 40 may be deactivated. The counter-measure circuit board 40 includes an energy generating unit 60.

The energy generating unit 60 comprises a power supply and energy storage devices such as capacitors. For example, the energy generating unit 60 comprises three large capacitors, for example, 2200 μF, to delivery a high energy trigger pulse to trigger actuators 62. A switching unit 64 is controlled by the microprocessor 54 and is connected to the energy generating unit 60. The switching unit 64 is a relay which is required to be energised before a trigger pulse is sent from energy generating unit 60 to the actuators 62. The actuators 62 are connected to the relay 64 via an output port 66.

The counter-measure circuit board 40 is controlled by the controller 40 sending an actuating signal via the serial ports 38 and 56 to the microprocessor 54 of the counter-measure circuit board 40. When the gas heads 16, 18 sense gas and this is detected by the controller 14, the controller 14 sends a signal serially to the counter- measure circuit board 40 that gas has been sensed. The signal from the controller 14 is an encrypted signal. The signal is a complex, digital algorithm which is sent multiple times and the microprocessor 54 of the counter-measure circuit board 40 needs to verify receipt of the signal. The counter-measure circuit board 40 sends a notification to the controller 14 that it has received a signal and the controller 14 needs to send the signal again before the counter-measure board 40 commences energising of the energy generating unit 60.

When a valid signal has been received by the counter-measure circuit board 40, the microprocessor 54 activates the energy generating unit 60 causing the capacitors to charge. The capacitors remain in a charged condition and the microprocessor 54 needs to actively energise the relay 64 before the capacitors discharge and send a trigger pulse to the actuators 62. This dual stage operation inhibits spurious activation of the actuators 62. The actuators 62 are connected to counter-measure units (not shown), for example, containers of neutralising gas, which are activated to release the gas to counteract the effect of the hydrocarbon gases detected in the ATM. In so doing, destruction of the ATM may be inhibited.

The counter-measure circuit board 40 is also operative to ensure that the actuators 62 are working. The microprocessor 54 generates a light constant current and voltage signal sent to the actuators 62. If either actuator 62 fails, a serial message is sent to the controller 14 to trigger the relay 42 that there is a problem. In addition, a message is displayed on the display 32 of the controller 14.

It is also to be noted that all signals are emulated through the serial port 15 of the controller to a remote location, for example, an alarm panel, a modem, or the like.

It is therefore an advantage of the invention that a system 10 is provided which enables hydrocarbon gases to be detected in confined volumes in a more accurate way than previously achieved. In particular, the use of at least two gas heads improves the accuracy of the system and inhibits the generation of false alarms. Also, because the gas heads are spaced from each other, a greater area of detection can be achieved. It will be appreciated by persons skilled in the art that numerous variations and/or modifications may be made to the invention as shown in the specific embodiments without departing from the scope of the invention as broadly described.

The present embodiments are, therefore, to be considered in all respects as illustrative and not restrictive.