GB2553289A

GB2553289A - Alarm system detector

Info

Publication number: GB2553289A
Application number: GB1614470.1A
Authority: GB
Inventors: Oconnell Michael; Galbraith Colin
Original assignee: Orisec Ltd
Current assignee: Orisec Ltd
Priority date: 2016-08-24
Filing date: 2016-08-24
Publication date: 2018-03-07
Anticipated expiration: 2036-08-24
Also published as: GB201614470D0; GB2553289B

Abstract

A detector 2 for an alarm system comprises a sensor module 4, a control module 6 and an output module 8. The sensor module 4 can be a motion detector or intrusion sensor or a glass-break detector and outputs a signal to the control module 6 indicative of a sensor state. The control module 8 communicates with the sensor module 4 and output module 8 via first and second electrical connections 10 and 12 respectively. The control module 6 can have a processor used to process signals from the sensor module 4 and output signals to the output module 8. Depending on the signals received from the control module 6 the output module 8 will control an electrical impedance across two contacts 14a and 14b with respect to specific values. The specific impedance values correspond to different sensor states. The impedance of the contacts 14a and 14b are monitored by a control panel to identify such conditions as an alarm state, a fault state, a tamper state, a masked state and a normal or healthy operating state. The output module 8 can be a digital potentiometer.

Description

(54) Title of the Invention: Alarm system detector

Abstract Title: Indicating a sensor output by controlling impedance across two electrical contacts (57) A detector 2 for an alarm system comprises a sensor module 4, a control module 6 and an output module 8. The sensor module 4 can be a motion detector or intrusion sensor or a glass-break detector and outputs a signal to the control module 6 indicative of a sensor state. The control module 8 communicates with the sensor module 4 and output module 8 via first and second electrical connections 10 and 12 respectively. The control module 6 can have a processor used to process signals from the sensor module 4 and output signals to the output module 8. Depending on the signals received from the control module 6 the output module 8 will control an electrical impedance across two contacts 14a and 14b with respect to specific values. The specific impedance values correspond to different sensor states. The impedance of the contacts 14a and 14b are monitored by a control panel to identify such conditions as an alarm state, a fault state, a tamper state, a masked state and a normal or healthy operating state. The output module 8 can be a digital potentiometer.

Figure 1

1/1

Figure 1

Alarm System Detector

The present invention relates to a detector for an alarm system. The present invention also relates to a method of operating a detector.

Many intruder alarm systems comprise detectors configured to sense the presence of motion, which may be indicative of an intruder. Such detectors are typically configured to communicate with a control panel of the alarm system. It is known for such a detector to comprise a pair of terminals which are connected to the control panel by wires, the detector comprising a relay (i.e. a switch) connected across the terminals such that the relay is closed when no motion is detected and the relay is open when motion has been detected. The control panel of such an alarm system is operable to detect when the relay is open or closed, such as for example by measuring a resistance across the terminals. Where the resistance across the terminals is low, this indicates that the relay is closed and therefore no motion has been detected. Where the resistance across the terminals is high, this indicates that the relay is open and therefore motion has been detected. In response to the opening of the relay, the alarm system may be configured to sound an alarm. It will be appreciated that in some situations the alarm system may not sound an alarm in response to the opening of the relay, such as for example when the alarm system is in an “unarmed” state.

In addition to detecting motion, some detectors are configured to detect when the detector has been tampered with. For example, the housing of the detector may comprise a microswitch which is arranged to open or close when the detector is tampered with (for example if a front cover of the detector is removed). Other known detectors are further configured to sense when the detector has been masked or covered in an attempt to prevent the detector from sensing motion. One disadvantage of such detectors is that, in order to communicate information relating to masking or tampering of the detector, multiple relays or switches may be required on the detector and multiple inputs may be required on the control panel.

It is an object of the present invention to obviate or mitigate one or more problems of the prior art, whether identified herein or elsewhere.

According to a first aspect of the invention there is provided a detector for an alarm system, the detector comprising: a sensor module operable to output a status signal indicative of a status of the detector; ,a control module configured to receive the status signal and output a control signal in dependence on the status signal; and an output module comprising a first electrical contact and a second electrical contact, the output module being configured to receive the control signal and to control an electrical impedance across the first electrical contact and the second electrical contact in dependence upon the control signal.

It will be appreciated that the impedance across the first and second electrical contacts is indicative of the status of the detector. The impedance across the first and second electrical contacts may therefore be measured so as to determine the status of the detector. The status of the detector may be, for example, that an intruder has or has not been detected, that a fault is present, that the detector has been tampered with, that the sensor module has been masked (i.e. by tape) or any combination of these. In use, the control module receives the status signal from the sensor module and may then determine a value of electrical impedance that is to be achieved across the first and second electrical contacts based upon the status of the detector, as determined using of the sensor module. The control module then outputs a control signal to the output module representative of a desired impedance value across the first and second electrical contacts. In response to the control signal, the output module adjusts and/or maintains the electrical impedance across the first and second electrical contacts so that the impedance matches the desired impedance value. The impedance across the first and second electrical contacts may then be measured by a control panel of the alarm system, the alarm system being configured to recognise that the measured amount of impedance across the first and second electrical contacts is indicative of the status of the detector. For example, different impedance values may correspond to different states of the detector. In response to the determination of the current status of the detector by the control panel, the control panel may cause an alarm of the alarm system to be activated.

The detector of the first aspect of the invention provides the advantage that the detector is easily configurable. As such, the detector may output a range of different values of impedance across the first and second electrical contacts without requiring replacement of any hardware. Instead, the control module may simply be programmed to output a specific value of impedance which is to be achieved across the first and second electrical contacts by the output module.

It will be appreciated that the sensor module is intended to mean a part of the detector that is operable to receive an input from an external stimulus. The sensor module may be, for example, a motion sensor, a vibration sensor, a magnetic sensor, a smoke detector, a glass break detector, a microwave detector or the like. Additionally or alternatively the sensor module may be configured to detect a tamper event, such as for example an attempt to remove the detector from its mounting. Additionally or alternatively the sensor module may be configured to detect a masking event (i.e. where the sensor is covered) and/or a fault with the sensor. It will further be understood that the status signal may be output by the sensor module either actively or passively. That is, the status signal may be obtained by the control module by measuring a property of the sensor module.

It will be appreciated that the control module is intended to mean a part of the detector that is operable to send, receive and process signals. For example, the control module may comprise any processor that is configured to receive the status signal from the sensor module, process the information encoded in the status signal, and output the control signal to the output module. It will be appreciated that the processor of the control module may comprise a microprocessor and/or analogue electronics. Additionally or alternatively, the control module may comprise memory.

It will be appreciated that the output module is intended to mean a part of the detector that is operable to set, maintain and adjust the electrical impedance across the first and second electrical contacts. For example the output module may comprise an electronic potentiometer, digital to analogue converter or the like.

In order to determine the impedance across the first and second electrical contacts, a potential difference (i.e. a voltage) may be applied across the electrical contacts and a resultant current flowing through the electrical contacts may be monitored (e.g. by a control panel of the alarm system). The impedance across the electrical contacts may then be determined from the applied voltage and the resultant current (e.g. using Ohm’s law). It will be appreciated that the current flowing across the first and second electrical contact may be either alternating or direct current. As such, it will be understood that the term electrical impedance is intended to mean the opposition to the flow of current in an electrical circuit of either alternating or direct current. Where the current flowing across the first and second electrical contacts is alternating current, the electrical impedance may comprise both a resistance and a reactance. Where the current flowing across the first and second electrical contacts is direct current, the impedance may comprise a resistance only.

The control module may be operable to store a set of electrical impedance values, each electrical impedance value corresponding to a state of the detector. It will be appreciated that the set of electrical impedance values is intended to mean a collection of data comprising a plurality of specific electrical impedance values, each electrical impedance value corresponding to a different state of the detector. For example, the control module may store an array comprising a column of states of the detector and a corresponding column of required electrical impedances. As such, each row of the array may store a state of the detector and a corresponding electrical impedance value.

The control signal may be generated based upon the electrical impedance value corresponding to the status of the detector. For example, where the electrical impedance value is a given number of Ohms, the control signal is generated to be a signal which is readable by the output module so as to cause the output module to adjust or maintain the impedance across the first and second electrical contacts to be that number of Ohms.

The control module may comprise a plurality of selectable communication schemes and generation of the control signal may be additionally dependent upon an active communication scheme of the control module. The detector provides the advantage that it is compatible with alarm system control panels originating from different manufacturers. For example, different control panels may interpret the same impedance as corresponding to a different state of the detector. Since the output module of the detector is able to adjust the electrical impedance across the first and second electrical contacts to a desired amount, the detector is able to emulate the electrical impedance across the first and second electrical contacts which would be expected by a given control panel for a given status of the detector.

As discussed above, it will be appreciated that the detector according to the first aspect of the invention is usable with a range of different control panels (i.e. from different manufacturers). Whilst all of the control panels may be configured to infer a state of the detector from a determined impedance across the first and second electrical contacts, each different control panel may interpret a given impedance across the first and second electrical contacts as corresponding to different states of the detector. For example, a first control panel may interpret an impedance across the first and second electrical contacts of 1 kD as an “alarm” status, whereas a second control panel may interpret an impedance of 2.2 kD as an “alarm” status. Each of the plurality of communication schemes may therefore correspond to a different type of control panel such that when the detector is used with a particular type of control panel and the corresponding communication scheme of the detector is selected, the detector is configured to output an impedance across the first and second electrical contacts which matches the values of impedance recognised by that control panel. That is to say, in the example given above, a first communication scheme of the control module would cause the detector to maintain an impedance of 1 kD across the first and second electrical contacts for an “alarm” status, whereas a second communication scheme of the control module would maintain an impedance of 2.2 kD across the first and second electrical contacts for an “alarm” status.

It will be understood that the active communication scheme of the control module is the communication scheme of the control module which is currently selected at the time that the status signal is received by the control module.

Each communication scheme may be selectable upon receipt of a user input signal by the control module. Since the communication scheme of the control module is selected based upon a user input signal, it will be appreciated that the communication scheme is selectable by a user. As such, the control module may be pre-programmed with a plurality of different sets of impedance values corresponding to the different states of the detector which are configured to be read by different control panels. During installation, the user may simply select which control panel they intend to use with the detector. This is advantageous as the user is not required to install or replace any physical components within the detector when it is to be used with different control panels.

It will be understood that a user input signal is intended to mean a deliberate signal from the user which tells the control module to change the active communication scheme of the control module. For example, the user input signal may be generated by a user-actuable switch which is pressed by the user. -Additionally or alternatively, the detector may comprise an anti-tamper module having one or more anti-tamper switches and the user input signal may be generated by actuation of one of the antitamper switches. In such embodiments the user-actuable switch may be one of the anti-tamper switches. It will be understood that the user input signal is distinct from the status signal.

The control module may store a plurality of sets of electrical impedance values, each set of electrical impedance values corresponding to one of the plurality of communication schemes. It will be appreciated that each one of the plurality of sets of electrical impedance values may comprise a plurality of electrical impedance values which each correspond to a different state of the detector. For example, the control module may store an array comprising a column of states of the detector and a plurality of corresponding columns of electrical impedance values. As such, each row of the array may store a state of the detector and a plurality of corresponding electrical impedance values.

The set of electrical impedance values may be selected based upon the active communication scheme of the control module. That is to say, the control module determines which communication scheme it is currently in and then determines which required electrical impedance should be output based on the status signal. Upon receiving the status signal from the sensor module, the electrical impedance value required may be selected from the column of electrical impedance values which corresponds to the current communication scheme of the control module.

The control module may comprise a first operating mode in which the communication scheme of the control module is selectable. It will be understood that the term “selectable” is intended to mean that the communication scheme of the control module may be changed. In addition to the first operating mode, the control module may comprise a second operating mode in which the communication scheme of the control module is not selectable. The control module may be configured to operate in the first operating mode during an initialisation time period which may start when the detector is powered up. For example, the detector may operate in the first operating mode for a period of time, for example 1 or 2 minutes, following power up. At the end of the initialisation time period the control module may switch to operation on the second operating mode.

The output module may be operable to control an electrical resistance across the first and second electrical contacts. For example, a control panel may apply a direct (i.e. non-alternating) current across the first and second electrical contacts of a definite value. The control panel may measure the potential difference (i.e. the voltage) across the first and second electrical contacts and determine a resistance value for the current and the voltage (for example using Ohm’s law). The resistance value may then be compared to a list of known reference values to determine the state of the detector.

The output module may comprise an electronic potentiometer. It will be appreciated that the electronic potentiometer is operable to vary the electrical impedance between two points based upon an electronic input. In contrast, a mechanical potentiometer is operable to vary the electrical impedance between two points based upon a mechanical input (e.g. via a knob). Such electronic potentiometers may comprise a digital to analogue converter and/or a resistor ladder. It will further be appreciated that such electronic potentiometers may be provided as circuit board mountable chips.

The output module may be configured to control the electrical impedance across the first electrical contact and the second electrical contact up to a value of at least 50 kQ. It will be appreciated that in addition to this value, the output module may be configured to provide infinite impedance across the first and second electrical contacts, such as for example by breaking the electrical circuit between the first and second electrical contacts.

The output module may be configured to adjust the amount of electrical impedance across the first electrical contact and the second electrical contact in discrete intervals. That is to say, the output module is operable to adjust the impedance across the first and second electrical contacts in steps. It will be appreciated that narrower intervals of impedance will provide finer precision over the output impedance across the first and second electrical contacts. Each interval may be within the range of 0.1- 0.3 kQ.

The detector may comprise a user-actuable switch and the user-actuable switch is configured to generate the user input signal. The detector may comprise a housing and the user-actuable switch may be a button positioned within the housing such that it is not accessible from an exterior of the housing. When the user-actuable switch is actuated by a user, the user-actuable switch will generate a user input signal which is received by the control module. In response to the user input signal, the control module may change the active communication scheme.

The detector may further comprise a light emitting module. The control module may be configured to control the light emitting module to display a light pattern, the light pattern indicating a communication scheme of the control module.

The control module may comprise a memory. The memory of the control module may comprise non-volatile memory. For example, the non-volatile memory may be read only memory.

According to a second aspect of the invention there is provided a method of operating a detector for an alarm system, the method comprising: receiving a status signal from a sensor module; generating a control signal in dependence upon the status signal; and controlling an electrical impedance across a first electrical contact and a second electrical contact in dependence upon the control signal.

The method may further comprise: receiving a user input signal; and selecting a communication scheme in dependence upon the user input signal; and the control signal may be generated in additional dependence upon the communication scheme.

The detector may be a detector according to the first aspect of the invention.

Embodiments of the invention will now be described, by way of example only, with reference to the accompanying drawing, in which:

Figure 1 is a schematic view of a detector in accordance with the present invention.

Figure 1 shows a detector 2 of an alarm system. The detector 2 comprises a sensor module 4, a control module 6 and an output module 8. The sensor module 4 is configured to detect an event associated with the presence of an intruder in the environment in which the detector 2 is installed. For example, the sensor module 4 may comprise a motion sensor that is configured to detect motion. Said motion sensor may be operable to sense infrared and/or microwave radiation. Additionally or alternatively, the sensor module 4 may comprise a glass break sensor configured to detect when a pane of glass has been broken, which may be indicative of an intruder attempting to break into a building. In general, it will be appreciated that the sensor module 4 may comprise any sensor, or any number of sensors, suitable for detecting an event associated with the presence of an intruder so as to determine that an intruder is present.

The control module 6 is operable to communicate with the sensor module 4 and the output module 8 via first and second electrical connections 10, 12 respectively. The first and second electrical connections 10, 12 may comprise a plurality of electrical wires configured to transmit signals and/or power between the sensor module 4, control module 6 and the output module 8. In an example embodiment, the control module 6 comprises a processor. As will be explained below, the processor is operable to process an incoming signal from the sensor module 4 and output a signal to the output module 8 in dependence thereon. It will be appreciated that the control module 6 may comprise any suitable signal processing elements. For example, the processor of the control module may comprise a circuit of analogue electronics, or may comprise a microprocessor. Alternatively or additionally, the control module 6 may comprise a memory. It will be appreciated that the memory of the control module 6 may comprise any suitable memory elements. For example, the memory of the control module 6 may comprise non-volatile memory, such as read only memory.

The output module 8 is configured to control an electrical impedance across two electrical contacts 14a, 14b. That is to say, the output module 8 is operable to set, adjust and/or maintain the impedance across the electrical contacts 14a, 14b to one of a plurality of specific impedance values. During use, the impedance across the electrical contacts 14a, 14b is monitored by a control panel (not shown) of the alarm system. As such, the value (i.e. the amount) of the impedance across the electrical contacts 14a, 14b may be used to communicate information relating to a status of the detector 2. For example, the control panel may be configured to interpret a first impedance value (for example 1 kD) as an “alarm” status, and a second impedance value (for example 2 kQ) as a “healthy” status (i.e. no alarm). The specific value of impedance across the electrical contacts 14a, 14b that is to be set or maintained by the output module 8 is determined by the control module 6 based upon the signal from the sensor module 4 and the type of control panel used.

In an example embodiment, the output module 8 comprises an electronic potentiometer operable to receive a signal from the control module 6 indicative of a required level of impedance and, in response to the signal, to adjust the impedance across the electrical contacts 14a, 14b accordingly. In order to provide such functionality, the electronic potentiometer may, for example, comprise a processor configured to receive the signal from the control module and a resistor ladder configured to provide a variable impedance across the electrical contacts 14a, 14b. Additionally or alternatively, the output module 8 may comprise a digital to analogue converter.

The electrical contacts 14a, 14b are connected to the output module 8 by a third electrical connection. In the example embodiment, the third electrical connection comprises a pair of wires 15a, 15b extending between the output module 8 and the electrical contacts 14a, 14b. The electrical contacts 14a, 14b are connectable to wires 16a, 16b which extend from the detector 2 to the control panel of the alarm system. It will be appreciated that electrical contact 14a may be considered to be a first electrical contact, and electrical contact 14b may be considered to be a second electrical contact (or vice versa).

In an example embodiment, electrical energy is delivered to the detector 2 via a pair of power supply lines 17a, 17b. The control module 6 distributes electricity from the supply lines 17a, 17b to the components of the detector 2, such as for example to the sensor module 4 and the output module 8 via the first and second electrical connections 10, 12. Additionally or alternatively, the detector 2 may comprise an internal power supply, such as for example a battery. In further alternative embodiments of the invention, the power supply lines 17a, 17b may be directly connected to a separate power supply than that of the control panel, such as for example to a mains electricity outlet. It will be appreciated that the power supply lines 17a, 17b may be bundled with the wires 16a, 16b such that the power supply lines 17a, 17b and wires 16a, 16b extend between the control panel and the detector 2 in a single conduit (e.g. within a single multicore cable).

The detector 2 comprises a housing 18 defining an interior containing the sensor module 4, the control module 6 and the output module 8. The housing 18 is configured to mount the detector 2 to a mounting surface, such as for example a wall or ceiling of a building. As such, the housing 18 may comprise a mounting, such as for example a bracket, configured to hold the detector 2 in a desired position relative to the mounting surface. In some embodiments, the mounting may be a separate component to the housing 18. It will be appreciated that where the sensor module 4 comprises a motion sensor, the housing 18 may further comprise a lens configured to permit the transmission of electromagnetic radiation (e.g. infrared light or microwave radiation) between the sensor module 4 and an exterior of the housing 18.

It will be appreciated that the housing 18 is configured to permit the wires 16a, 16b to reach the electrical contacts 14a, 14b. The electrical contacts 14a, 14b may be enclosed by the housing 18 such that they are not accessible from an exterior of the housing 18. For example, the electrical contacts 14a, 14b may be defined by a terminal block located in the interior of the housing 18. The housing 18 may comprise two separable housing portions configured to separate so as to permit access to the interior of the housing 18, and therefore also permit access to the first and second electrical contacts 14a, 14b, for example during installation and/or maintenance. Additionally, the housing 18 may define an aperture configured to permit the wires 16a, 16b to enter the interior of the housing 18 so as to reach the first and second electrical contacts 14a, 14b (or likewise for the power lines 17a, 17b to reach the control module 6). For example, the housing 18 may comprise a frangible tab configured to break away from the housing 18 so as to leave an aperture for the receipt of the wires 16a, 16b (and/or the power lines 17a, 17b).

The sensor module 4 further comprises an anti-tamper module 22 configured to detect a tamper event. A tamper event may be, for example, an attempt by an intruder to gain access to an interior of the detector 2 by separating the housing portions of the housing 18. To detect such tamper events, the anti-tamper module 22 may comprise one or more anti-tamper switches which are actuated by a tamper event. When a tamper event has been detected, the sensor module 4 will output a signal to the control module 6 to indicate that the detector 2 has been tampered with. In turn, this tamper event may be communicated to the control panel and may result in the sounding of an alarm by the control panel. The communication of such tamper events (and other states of the detector 2) is achieved via the output module 8 and electrical contacts 14a, 14b, as described below. It will be appreciated that the anti-tamper module 22 may be part of the sensor module 4, however in alternative embodiments of the invention the anttamper module 22 may be separate to the sensor module 4. In such embodiments, the anti-tamper module 22 may be operable to communicate directly with the control module 6 (and not via the sensor module 4). In such embodiments, it will be appreciated that although the anti-tamper module 22 does not form part of the sensor module 4, because the anti-tamper module 22 is operable to sense a tamper event, the anti-tamper module 22 may still be considered part of, or an auxiliary part of, the sensor module 4.

During use, the sensor module 4 outputs a status signal to the control module 6 indicative of a status of the sensor module 4 (and therefore the detector 2). The status of the sensor module 4 may indicate one of a plurality of different states of the sensor module 4. That is to say, the plurality of different states of the sensor module 4 may each correspond to a different one of a plurality of possible operating conditions of the sensor module 4, whereas the status of the sensor module 4 may correspond to whichever one of the plurality of different states of the sensor module 4 is currently in. The different states may comprise:

an “alarm” state, indicating that the sensor module 4 has detected an intruder; a “fault” state, indicating that the detector 2 is damaged in some way and may not be functioning normally;

a “tamper” state, indicating that the detector 2 has been tampered with; a “mask” state, indicating that the detector 2 has been covered such that it is no longer able to detect the presence of an intruder (e.g. where an obstruction is placed over the lens); or a “healthy” state, indicating that none of the above states are active.

It will be appreciated that the sensor module 4 may communicate the status signal to the control module 6 either actively or passively. For example, the status signal may be a signal which originates from and is determined by the sensor module 4 (i.e. active communication of the status signal). Alternatively the status signal may be a signal which originates from the control module 6 which is configured to read the status of the sensor module 4 (i.e. passive communication of the status signal). It will be appreciated that the status signal may be sent continuously, intermittently, or periodically.

The control module 6 receives the status signal, and determines a value of the impedance that is to be maintained across the electrical contacts 14a, 14b, in dependence upon the status signal. In order to determine the value of impedance that is to be maintained, the control module 6 may comprise a memory (e.g. read-only memory) which is configured to store a plurality (i.e. a set) of impedance values corresponding to different states of the sensor module 4. The control module 6 then outputs a control signal to the output module 8 based upon the received status signal (which is indicative of the status of the sensor module 4). The control signal is received by the output module 8 and causes the output module 8 to regulate (i.e. adjust or maintain) the impedance across the first and second electrical contacts 14a, 14b to the value of impedance determined by the control module 6.

The control panel is configured to measure the value of the impedance between the first and second electrical contacts 14a, 14b. In particular, the control panel is operable to interpret the current status of the sensor module 4 based upon the measured impedance across the first and second electrical contacts 14a, 14b. Depending upon the interpreted status of the sensor module 4, the control panel may be configured to react to the interpreted status by sounding an alarm. It will be appreciated that the control panel may be configured to measure the impedance across the first and second electrical contacts 14a, 14b continuously, intermittently or periodically. The control panel may be configured to measure the impedance across the first and second electrical contacts 14a ,14b by applying a potential difference (i.e. a voltage) across the electrical contacts 14a, 14b and monitoring a resultant current flowing across the electrical contacts 14a, 14b. The impedance across the electrical contacts 14a, 14b may then be determined from the applied voltage and the resultant current (e.g. using Ohm’s law). It will be understood that the control panel is configured to respond to the measured impedance value across the electrical contacts 14a, 14b on the basis of its interpretation of which state of the detector 2 the measured impedance value corresponds to.

It will be appreciated that different control panels may be configured to interpret the impedance across the first and second electrical contacts 14a, 14b of the detector 2 differently. That is to say, a given impedance may correspond to different states of the sensor module 4 when read by different control panels. So that the detector 2 is usable with a variety of different control panels, the control module 6 is provided with a plurality of different communication schemes, each communication scheme corresponding to a different type of control panel. Each communication scheme comprises a plurality (i.e. a set) of values of impedance, each value of impedance corresponding to a different state of the sensor module 4. In order to achieve this, the memory of the control module 6 may store an array of impedance values which correspond to different states and communication schemes.

An example is now described with three communication schemes with reference to table 1 below.

Table 1:

State	Impedance (kQ)
Scheme A	Scheme B	Scheme C
Alarm	6.9	11.5	6.9
Fault	4.4	16.7	9.0
Tamper	Open (infinite)	Open (infinite)	Open (infinite)
Mask	9.1	23.5	13.7
Healthy	2.2	4.7	4.7

In the above example, where the active (i.e. current) communication scheme of the control module 6 is scheme B and an intruder is detected, the control module 6 will output a control signal to the output module 8 so as to cause the output module 8 to adjust the electrical impedance across the electrical contacts 14a, 14b to a value of

11.5 kQ. If the current communication scheme of the control module 6 was either scheme A or scheme C, the electrical impedance across the contacts 14a, 14b would be adjusted to 6.9 kQ. It will be appreciated that the values of impedance given in the table above are for example only and are not intended as limiting on the invention. It will further be appreciated that the control module 6 may comprise substantially any number of communication schemes. It will be appreciated that the data exemplified by Table 1 may be stored in the memory of the control module 6 in any convenient way (e.g. as an array, list, table etc.).

The control module 6 can operate in either a first operating mode in which the communication scheme of the control module 6 can be changed or a second operating mode in which the communication scheme of the control module 6 cannot be changed. The control module 6 may be configured to operate in the first operating mode during an initialisation time period which starts when the detector 2 is powered up. For example, the detector 2 may operate in the first operating mode for a period of time, for example 1 or 2 minutes, following power up. By powering up the detector 2, it is meant that the detector 2 is connected to a power supply, for example by connecting the pair of power supply lines 17a, 17b to a power supply. At the end of the initialisation time period the control module 6 may switch to operation in the second operating mode.

The initialisation time period may end at the end of the period of time following power up. Optionally, if sooner, the initialisation time period may end upon closure of an antitamper switch that forms part of the anti-tamper module 22. That is, it may only be possible to change the communication scheme for a predetermined time period following power up and provided that the anti-tamper switch is open. The anti-tamper switch that forms part of the anti-tamper module 22 may close when the two separable housing portions of the housing 18 are brought together.

The control module 6 is configured to select the communication scheme in response to the actuation of a user-actuable switch 26 (e.g. a push button) located within the interior of the housing 18. The switch 26 is in electronic communication with the control module 6. Actuation of the switch 26 sends a user input signal to the control module 6 as an electrical pulse, in response to which the control module 6 may select another communication scheme. In particular, the control module 6 may store the communication schemes in a list or sequence, and in response to each actuation of the switch 26 the control module may select the next communication scheme in the list or sequence.

In use, the detector is connected to a control panel of an alarm system. Typically, such control panels are operable in two different operating modes: a first operating mode (often referred to in the art as an “engineer mode”); and a second, live operating mode.

When the control panel is in the first operating mode the housing portions of the housing 18 can be separated and the switch 26 can be accessed so that the communication scheme may be changed without triggering an alarm. For example, the user may separate the portions of the housing 18, causing the anti-tamper module 22 to activate, and the output module 8 to change the impedance across the electrical contacts 14a, 14b to a value indicative of a “tamper” status. However, because the control panel is in the first operating mode (i.e. the engineer mode) the control panel will ignore the tamper status of the detector 2 and will not cause an alarm to sound. As such, the switch 26 (which may be inside the detector 2) can be accessed and the communication scheme of the control module 6 can be selected.

Additionally or alternatively, the anti-tamper module 22 may be configured to generate the user input signal when the control module 6 is in the first operating mode (for example during the initialisation period). For example, the anti-tamper module 22 may comprise one or more anti-tamper switches. When the control module 6 is in the second operating mode, actuation of the anti-tamper switches may cause the control module 6 to adjust the electrical impedance across the electrical contacts 14a, 14b to a value that indicates to the control panel that the detector 2 has been tampered with. However, when the control module 6 is in the first operating mode, actuation of the anti-tamper switches may cause the control module 6 to change the communication scheme of the control module 6. It will be appreciated that in such embodiments, the switch 26 may be an anti-tamper switch of the anti-tamper module 22, and the detector 2 may not comprise an additional switch for the user input signal.

Generally, it will be appreciated that in alternative embodiments of the invention the operating mode of the control module 6 may be selected in any suitable manner, and is not limited to the examples contained herein.

The detector 2 further comprises a light emitting module 27 in electrical communication with the control module 6. In the example embodiment, the light emitting module 27 comprises three light emitting diodes (LEDs) 28a, 28b, 28c which are electrically connected to the control module 6. The light emitting module 27 is configured to communicate information from the control module 6 to a user by activating or deactivating the LEDs 28a, 28b, 28c. As such, the light emitting module 27 may be configured such that it is visible from an exterior of the housing 18. For example, the light emitting module 27 may be positioned behind a light-transmitting portion of the housing 18 such as a lens portion of the housing 18. The lens may be configured to transmit light from the light emitting module 27 to the user.

During normal use (for example when the control module 6 is operating in the second operating mode), the light emitting module 27 may be configured to display information relating to the sensor module 4. For example, a first LED 28a may be activated in response to movement detection by an infrared sensor of the sensor module 4, a second LED 28b may be activated in response to movement detection by a microwave sensor of the sensor module 4, and a third LED 28c may be activated when both the infrared and microwave sensors have detected movement. It will be appreciated that in some embodiments of the invention, the light emitting module 27 may comprise a display screen instead of, or in addition to, the LEDs 28a, 28b, 28c. It will further be appreciated that the LEDs 28a, 28b, 28c may be different colours.

When the control module 6 is operating in the first operating mode, in response to the actuation of the switch 26, the light emitting module 27 is configured to display a pattern representative of the selected communication scheme of the control module 6. The pattern may be a spatial pattern. For example, at least one of the LEDs 28a, 28b, 28c may be activated (thus permitting 8 different communication schemes to be identified). Additionally or alternatively, the pattern may be a temporal pattern. For example, at least one of the LEDs 28a, 28b, 28c may flash at a specific rate or for a specific length / number of times. Where the light emitting module 27 comprises a display screen, the display screen may simply display the selected communication scheme as text.

It will be appreciated that the output module 8 may be configured to control the impedance across the electrical contacts 14a, 14b to substantially any value of impedance within an operating range such that the range of possible values of impedance achievable by the output module 8 is substantially continuous in that operating range. Alternatively, the output module 8 may be configured to control the impedance across the electrical contacts in discrete steps. The size of the discrete steps may for example be within the range 0.1 - 0.3 kD. However, it will be appreciated that any suitable step size may be used. In the present embodiment the output module 8 may be configured to control the impedance across the electrical contacts 14a, 14b up to a nominal maximum impedance of 50 kD. However, it will be appreciated that any suitable maximum impedance may be used. Furthermore, in addition to the nominal maximum impedance it will be appreciated that the output module 8 may be configured to provide an infinite impedance across the electrical contacts 14a, 14b by breaking the electrical circuit formed by the output module 8 across the electrical contacts 14a, 14b (i.e. such that the electrical contacts 14a, 14b are not electrically connected).

As explained above, in an example embodiment, the output module 8 comprises an electronic potentiometer operable to receive a signal from the control module 6 indicative of a required level of impedance and, in response to the signal, to adjust the impedance across the electrical contacts 14a, 14b accordingly. For such embodiments, the range of possible impedances that can be achieved across the electrical contacts 14a, 14b by the output module 8 is dependent on the type of electronic potentiometer used. In one example embodiment, the electronic potentiometer is the MCP41HV51503E/ST available from Microchip Technology, Inc. of the US. This is a 50 kQ digital potentiometer with an 8-bit resolution, i.e. it comprises 256 resistance taps of 195 Ω each. In this embodiment, the output module 8 is therefore operable to control the impedance across the electrical contacts 14a, 14b in discrete steps of 0.195 kQ up to a maximum impedance of 50 kQ.

It will therefore be appreciated that the value of impedance across the electrical contacts 14a, 14b is set by the control module 6 based upon both the current status of the detector 2 and the communication scheme of the control module 6, the communication scheme of the control module 6 being indicative of the type of control panel that the detector 2 is in communication with. As such, the detector 2 may be used with a variety of different control panels. It will be appreciated that this functionality may permit a user of the detector 2 to upgrade or change the control panel of the alarm system without having to also change the detectors when a new control panel is installed, the detectors merely need to be re-configured so as to operate in an appropriate communication scheme for the new control panel.

It is a known disadvantage of the prior art that where a prior art detector is to be used with a different control panel, electro-mechanical components within the prior art detector may need to be changed or recalibrated. For example, the prior art detector may comprise a series of electrical resistors which may need to be replaced where the prior art detector is used with a different control panel. Some prior art detectors are provided with one or more arrays of resistors which are selectable via one or more jumper switches. For example, a separate array and jumper switch may be provided for each of the alarm, tamper, mask, fault and healthy states of the detector. However, such arrangements require a large number of redundant resistors, which increases the cost and complexity of the detector. Furthermore, such arrangements can be bulky thus increasing the size of the detector. The detector 2 of the present invention avoids such disadvantages by being operable to change the electrical impedance across the contacts 14a, 14b without the replacement or recalibration of any physical components.

While specific embodiments of the invention have been described above, it will be appreciated that the invention may be practiced otherwise than as described. The descriptions above are intended to be illustrative, not limiting. Thus it will be apparent to one skilled in the art that modifications may be made to the invention as described without departing from the scope of the claims set out below.

Claims

CLAIMS:

1. A detector for an alarm system, the detector comprising:

a sensor module operable to output a status signal indicative of a status of the detector;

a control module configured to receive the status signal and output a control signal in dependence on the status signal; and an output module comprising a first electrical contact and a second electrical contact, the output module being configured to receive the control signal and to control an electrical impedance across the first electrical contact and the second electrical contact in dependence upon the control signal.

2. A detector according to claim 1, wherein the control module is operable to store a set of electrical impedance values, each electrical impedance value corresponding to a state of the detector.

3. A detector according to claim 2, wherein the control signal is generated based upon the electrical impedance value corresponding to the status of the detector.

4. A detector according to any preceding claim, wherein the control module comprises a plurality of selectable communication schemes and wherein generation of the control signal is additionally dependent upon an active communication scheme of the control module.

5. A detector according to claim 4, wherein each communication scheme is selectable upon receipt of a user input signal by the control module.

6. A detector according to claim 4 or 5, wherein the control module stores a plurality of sets of electrical impedance values, each set of electrical impedance values corresponding to one of the plurality of communication schemes.

7. A detector according to claim 6, wherein one of the plurality of sets of electrical impedance values is selected based upon the active communication scheme of the control module.

8. A detector according to any of claims 4 to 7, wherein the control module comprises a first operating mode in which the communication scheme of the control module is selectable.

9. A detector according to any preceding claim, wherein the output module is operable to control an electrical resistance across the first and second electrical contacts.

10. A detector according to any preceding claim, wherein the output module comprises an electronic potentiometer.

11. A detector according to any preceding claim, wherein the output module is configured to control the electrical impedance across the first electrical contact and the second electrical contact up to a value of at least 50 kQ.

12. A detector according to any preceding claim, wherein the output module is configured to adjust the amount of electrical impedance across the first electrical contact and the second electrical contact in discrete intervals.

13. A detector according to any preceding claim, wherein the detector comprises a user-actuable switch and wherein the user-actuable switch is configured to generate the user input signal.

14. A detector according to any preceding claim, wherein the detector further comprises a light emitting module.

15. A detector according to claim 14, wherein the control module is configured to control the light emitting module to display a light pattern, the light pattern indicating a communication scheme of the control module.

16. A detector according to any preceding claim, wherein the control module comprises a memory.

17. A detector according to claim 16, wherein the memory of the control module comprises non-volatile memory.

18. A method of operating a detector for an alarm system, the method comprising: receiving a status signal from a sensor module;

generating a control signal in dependence upon the status signal; and 5 controlling an electrical impedance across a first electrical contact and a second electrical contact in dependence upon the control signal.

19. A method according to claim 18, wherein the method further comprises: receiving a user input signal; and

10 selecting a communication scheme in dependence upon the user input signal;

wherein the control signal is generated in additional dependence upon the communication scheme.

20. A method according to either of claims 18 or 19, wherein the detector is a 15 detector according to any of claims 1 to 17.

Intellectual

Property

Office

Application No: GB1614470.1 Examiner: Keaton Hill