FIELD OF THE INVENTION

The present invention relates to an alarm system having a control panel and a plurality of alarm units , each of the alarm units being configured to generate an alarm .

BACKGROUND OF THE INVENTION

It is normal practice in some emergency systems such as fire alarm systems to have electrical circuits with multiple alarm units connected in each circuit . Each alarm unit may be configured to generate an alarm ( e . g . an audible and/or visual signal ) in case of an emergency . A central control panel may control power supply to the control units , in order to control activation of the alarm units . For safety purposes , it is a requirement for alarm systems that the alarm units be tested periodically to ensure that they are working properly . Testing requirements for alarm systems are regulated in many countries .

The present inventors have found that a drawback with the testing of alarm units in such alarm systems is that this can be very disruptive to occupants of the building , due to the loud alarm noises produced by the alarm units during testing . This can sometimes result in a frequency with which testing is performed to be reduced, which could lead to faults in the system not being detected . Another difficulty with the testing of alarm systems is that alarm units are often installed across a large site . Because of this , it can take a long time to check that each alarm unit is functioning properly, as an engineer must walk around the site to visually and audibly inspect each of the alarm units . This means that the central control panel that activates the alarm units may need to be activated for a large amount of time , to enable the engineer to inspect all of the alarm units .

In some cases , alarm units are configured into zones so that they can be tested in smaller groups . However, the testing of alarm units can still be disruptive and time consuming, as testing efficiently by zone requires an engineer to remain by the control panel to activate the alarm units in each zone while another engineer walks around and checks each alarm unit while they are activated .

SUMMARY OF THE INVENTION

At its most general , the present invention provides an alarm system having a plurality of alarm units , and a central control panel for controlling activation of the alarm units . Each alarm unit includes a wireless communication interface , so that it can receive wireless signals from a user device ( e . g . a mobile phone or the like ) . In this manner , each alarm unit may be individually controlled wirelessly via the user device .

Advantageously, this may enable each of the alarm units to be tested individually, by wirelessly triggering a test mode of an individual alarm unit via the user device . This may avoid having to activate all of the alarm units simultaneously at the control panel , and leaving the alarm units on whilst an engineer walks around an entire site to inspect all of the alarm units . As a result , testing of the alarm system may be far less disruptive , as the duration for which each alarm unit is activated for testing can be greatly reduced . In particular, as only a single alarm unit may be activated at a time for testing, occupants of the building that are not in the vicinity of the alarm unit that is being tested may not be disrupted .

Furthermore , wireless communication between the user device and the alarm units may be used to program and/or modify settings of individual alarm units . For instance , the user device may be used to set settings of an alarm unit such as alarm tone , alarm volume , or flash options ( e . g . where the alarm unit includes a light source ) . Conventionally, such settings in an alarm unit are set manually via a mechanical switch, such as a Dual Inline witch ( DIL switch) , in the alarm unit . This requires gaining access to the inside of the alarm unit , which may be difficult as this may involve interfering with any screws and seals that were fixed during installation of the alarm unit . As a result , accessing the inside of the alarm unit to modify settings of a conventional alarm unit could compromise the mechanical integrity or Ingress Protection ( IP ) rating of the alarm unit . In contrast , as the invention uses wireless communication for programming settings of the alarm units , integrity of the alarm units need not be compromised in order to program the alarm units . This may facilitate programming the alarm units , as well as improve an overall safety and reliability of the alarm system.

Another drawback of conventional alarm units is that , once the mechanical switch in the alarm unit has been operated to set new settings , the new settings cannot be tested without returning to the control panel and activating all of the alarm units in the alarm system, which may be highly disruptive . The alarm system of the invention addresses this drawback, by enabling settings of individual alarm units to be programmed and tested wirelessly . Thus , the setting and testing of new settings for an alarm unit may be far less disruptive compared to conventional alarm systems .

According to a first aspect of the invention, there is provided An alarm system comprising : a plurality of alarm units , each alarm unit being configured to generate an alarm; and a control panel configured to control power supplied to the plurality of alarm units ; wherein each of the plurality of alarm units comprises a wireless communication interface for receiving a control signal transmitted by a user device , and a controller configured to trigger a test mode of the alarm unit in response to receipt of the control signal.

The alarm system may be any suitable type of alarm system, which is configured to cause the plurality of alarm units to generate an alarm when a predetermined condition is detected. For example, the alarm system may be a fire alarm system, which is configured to cause the plurality of alarm units to generate an alarm when a fire is detected (e.g. via a smoke detector) . Other types of alarm systems include burglar alarm systems (e.g. which are configured to generate an alarm in case of intrusion into an area) , or atmosphere-monitoring alarm systems (e.g. which are configured to generate an alarm in case of oxygen deficiency in an area, and/or unsafe levels of a particular gas in an area) .

Each alarm unit is configured to generate an alarm. Each alarm unit may comprise an alarm generation module for generating the alarm. The alarm generated by an alarm unit may comprise an audible alarm signal and/or a visual alarm signal. For example, the alarm generation module of an alarm unit may comprise a sounder (e.g. speaker) for generating an audible alarm signal, and/or a light source or display for generating a visual alarm signal. In some cases, all of the plurality of alarm units may be identical, i.e. they may all be configured to generate a same type of alarm. However, in other cases, the alarm units need not be identical, e.g. the alarm system may include alarm units which are configured to generate different types of alarms .

The plurality of alarm units may be arranged at different locations across a site (e.g. in a building) , so that people at the different locations in the site may be alerted.

The control panel is configured to control power supplied to the plurality of alarm units. In this manner, the control panel may control when the plurality of alarm units generate an alarm, e.g. by controlling the power supplied to the plurality of alarm units. As an example, control of the power supplied to the plurality of alarm units may include control of a polarity of one or more voltages supplied to the plurality of alarm units , and/or a magnitude of the power supplied to the plurality of alarm units .

The control panel may be configured to activate an alarm mode of the alarm system when a predetermined condition is detected, wherein when the alarm mode is activated, each of the plurality of alarm units generates an alarm .

The alarm system may comprise one or more power supplies which are configured to supply power to the plurality of alarm units via one or more wired connections ( e . g . power supply lines or cables ) . Providing wired power supply to the alarm units may serve to improve a reliability of the alarm system .

In some cases , the control panel may comprise a power supply which is configured to supply power to the plurality of alarm units . Then, the control panel may be connected ( e . g . via a wired connection) , to each of the plurality of alarm units in order to supply power to the alarm units . Alternatively, the alarm system may comprise one or more power supplies that are external to the control panel , the one or more power supplies being configured to supply power to the plurality of alarm units ( e . g . via one or more wired connections ) . Then, the control panel may be communicatively coupled to the one or more power supplies ( e . g . via a wired or wireless connection ) , so that it can control power delivered to the plurality of alarm units by the one or more power supplies . Thus , regardless of whether the power supplied to the alarm units is provided directly by the control panel or not , the control panel acts to control the power supplied to the alarm units .

The control panel may include any suitable electronics for controlling the power supplied to the plurality of alarm units . For example , the control panel may include a microcontroller or computing device configured to execute software code for controlling the power supplied to the plurality of alarm units .

The alarm system may further comprise one or more detectors , each of which is communicatively coupled to the control panel . Each detector may be configured to detect a predetermined condition, and transmit a detection signal to the control panel in response to detecting the predetermined condition . Then, upon receipt of a detection signal from one of the detectors , the control panel may be configured to trigger an alarm mode of the alarm system . For example , where the alarm system is a fire alarm system, the plurality of detectors may comprise smoke detectors , temperature sensors , and/or any other suitable type of detector for detecting a fire outbreak . Where the alarm system is a burglar alarm system, the plurality of detectors may, for example , comprise motion sensors . Where the alarm system is an atmospheremonitoring alarm system, the plurality of detectors may, for example , comprise oxygen-level sensors and/or sensor for detecting other types of gas .

Additionally or alternatively to the detectors , the alarm system may include one or more switches for manually triggering the alarm mode of the alarm system.

Each of the plurality of alarm units comprises a wireless communication interface , so that it can receive control signals transmitted wirelessly from a user device . The wireless communication interface may be any suitable type of interface that enables such wireless communication . As an example , the wireless communication interface may comprise a near-field-communication (NFC ) interface , a Bluetooth ® interface , or a Wi-Fi interface , to enable wireless communication with the alarm unit . In some cases , the wireless communication interface may comprise a photodetector ( e . g . a photodiode ) , e . g . where the control signal is in the form of a light signal or an infrared signal . In other cases , the wireless communication interface may comprise a sound detector ( e . g . a microphone ) , e . g . where the control signal is in the form of a sound wave , for instance at ultrasound frequencies .

Following receipt of a control signal from a user device at the wireless communication interface in one of the alarm units , the controller in the alarm units is configured to trigger the test mode of that alarm unit . In this manner, the test mode of an individual alarm unit may be trigger wirelessly .

The wireless communication interface may be configured to convey information indicative of the received control signal to the controller . In some cases , the wireless communication interface may comprise a decoder which is configured to decode the received control signal and put it in a suitable format prior to transmitting it to the controller .

The test mode of an alarm unit may be a mode which enables an engineer to verify that the alarm unit is functioning properly . For example , the test mode of an alarm unit may comprise generating an alarm by that alarm unit . In this manner , it is possible to ensure that the alarm generation module of the alarm unit is functioning properly, and that the alarm unit is properly connected to its power supply .

The controller of an alarm unit may be configured to trigger the test mode of the alarm unit in various different ways . For example , the controller may be configured to control or operate one or more components ( e . g . a switch, variable resistor, or the like ) of an electrical circuit in the alarm unit to trigger the alarm mode . The controller may comprise a microcontroller or any other suitable type of processing unit which is configured to trigger the test mode in response to receipt of the control signal .

The user device may be any device which is configured to wirelessly transmit a control signal to an alarm unit . In particular, the user device may comprise a wireless communication interface that is capable of wirelessly communicating with the wireless communication interfaces in the alarm units . As an example , the user device may comprise a smartphone or other personal computing device having suitable software installed thereon . Alternatively, the user device may comprise an electronic device such as a remote control .

The user device may comprise a user interface for receiving an input from a user . In response to receiving an input from the user , the user device may be configured to transmit a control signal to one of the alarm units to trigger the alarm mode of the alarm unit . For example , the user device may comprise a button for triggering the test mode of an alarm unit .

In some embodiments , the user device may be considered as part of the alarm system, i . e . the alarm system may further comprise the user device .

Each of the plurality of alarm units may be configured to store a respective identifier . This may facilitate identifying an individual alarm unit amongst the plurality of alarm unit . For instance , the user device may be able to identify an alarm unit based on the unique identifier stored in that alarm unit . This may also facilitate controlling a desired one of the plurality of alarm units , by communicating with the alarm unit having a corresponding unique identifier . Storing a unique identifier in each of the plurality of alarm units may also facilitate logging test data relating to instances when the alarm units were tested, as test data corresponding to a particular alarm unit may be associated with its unique identifier .

Each alarm unit may comprise a memory ( e . g . a nonvolatile memory) in which its unique identifier is stored . In some embodiments , each alarm unit may be configured to transmit its unique identifier to the user device via the wireless communication interface , e . g . in response to a query received from the user device . The alarm system may be configured to record test data relating to instances when the test mode of any of the plurality of alarm units was triggered. In this manner, the system may maintain a record of the times when each of the alarm units was tested. This may facilitate monitoring of testing that is carried out across the system, e.g. so that an engineer may ensure that all of the alarm units are being tested regularly. Test data relating to instances when an alarm unit was tested may include information indicative of a date and/or time when the test mode of the alarm unit was triggered, a user device that triggered the test mode (e.g. an identifier of the user device) , a duration for which the test mode was triggered, one or more settings of the alarm unit during the test mode (e.g. alarm tone, volume, etc. ) , or any other relevant information. In some cases, the test data may include a result of the test mode, e.g. an indication of whether an alarm was successfully generated or not following triggering of the test mode. Test data may also include data relating to a detected property of an alarm generated by an alarm unit during its test mode. For example, the test data may include a detected volume of the alarm, a detected sound pressure level (e.g. in dB or dBA) , or a detected frequency of the alarm. Where the alarm comprises a visual alarm (e.g. a flashing light) , the test data may include a detected intensity of the visual alarm. The test data may be stored in different ways at various locations in the alarm system, examples of which are given below.

Each of the plurality of alarm units may be configured to store test data relating to instances when the test mode of that alarm unit was triggered. In other words, each alarm unit may maintain a record (or log) of instances when that alarm unit was tested. Storing test data directly in each alarm unit may provide a convenient and reliable way of keeping a record of tests performed on that alarm unit. In particular, this may facilitate verifying when an alarm unit was last tested, e . g . by reading the test data stored in the alarm unit .

Each alarm unit may comprise a memory ( e . g . non-volatile memory) in which the test data for that alarm unit is stored . Following triggering of the test mode of the alarm unit , the controller may be configured to store test data relating to triggering of the test mode in the memory . In this manner, the test data may be automatically recorded by the alarm unit .

Each of the plurality of alarm units may configured to transmit , via the wireless communication information, test data stored therein to a user device . This may facilitate accessing the test data stored in the alarm unit , as it avoids having to physically access the memory inside the alarm unit . As a result , an engineer may easily review test data for the alarm unit when on site . The alarm unit may be configured to transmit the test data to the user device in response to a query received from the user device . For example , in response to receipt of a query from the user device at the wireless communication interface , the controller may be configured to cause transmission of stored test data to the user device via the wireless communication interface .

In some embodiments , the alarm system may comprise a database in which the test data for all of the plurality of alarm units is stored . In this manner, test data for the entire alarm system may be stored centrally in a single database , which may facilitate access to the test data . The database may associate the test data corresponding to each alarm unit with the unique identifier for that alarm unit . The database may be stored in a memory of the alarm system .

The alarm system may further comprise a remote server, wherein the remote server is configured to store test data relating to instances when the test mode of any of the plurality of alarm units was triggered . For instance , the remote server may store the database mentioned above . In this manner, the test data for the alarm system may be accessed via a computing device which is in communication with the remote server ( e . g . via the internet ) . The remote server may be a computing system that is connected to the internet , and comprising a memory for storing the test data . As an example , the remote server may be a cloud server .

The test data may be conveyed to the remote server in a variety of ways . In one example , where the user device is part of the alarm system, the user device may be configured to , following transmission of a control signal to an alarm unit to trigger the test mode of the alarm unit , transmit test data relating to triggering of the alarm mode of the alarm unit to the remote server . The test data transmitted by the user device may comprise the unique identifier of the alarm unit in which the test mode was triggered . In this manner, each time the user device triggers the test mode in an alarm unit , corresponding test data may be transmitted to the remote server , such that the remote server may maintain a record of all the instances when test modes were triggered across the alarm system. The user device may transmit the test data to the remote server using any suitable communication means , e . g . via a wireless communication network such as Wi-Fi or a mobile network ( e . g . 2G, 3G, 4G, 5G) .

The user device may comprise a user interface for receiving an input from a user that is indicative of a test result of triggering the test mode in one of the alarm units . For example , a user may indicate whether an alarm was successfully generated by the alarm unit during the test mode . The user device may be configured to transmit information indicative of the test result to the remote server .

In some cases , the user device may be configured to record test data relating to instances when the test mode of one or more of the plurality of alarm units was triggered . For example , the user device may be configured to , following transmission of a control signal to an alarm unit to trigger the test mode of the alarm unit , record test data relating to triggering of the alarm mode of the alarm unit . The test data may include the unique identifier corresponding to the alarm unit . Thus , each time the user device triggers the test mode in an alarm unit , test data may be automatically recorded in the user device , thus facilitating recording of test data . As a result , a record of tests performed with the user device may be maintained in the user device , which may facilitate checking historical test data whilst on site .

The test data recorded by the user device may comprise data relating to a property of an alarm generated by an alarm unit during its test mode of that alarm unit . For instance , following transmission of a control signal to an alarm unit to trigger the test mode of the alarm unit , the user device may be configured to detect a property of the alarm generated by the alarm unit . As an example , the user device may be configured to detect a volume or sound pressure level of the alarm ( e . g . via a microphone in the user device ) . Where the alarm comprises a visual alarm ( e . g . a flashing light ) , the user device may be configured to detect a light intensity of the visual alarm ( e . g . via a photodetector or camera in the user device ) .

Any combination of the different ways of recording test data, and the different locations at which test data can be recorded, can be used in embodiments of the invention .

For each of the alarm units , in response to receipt of the control signal from the user device , the controller may be configured to authenticate the user device prior to triggering the test mode of the alarm unit . This may ensure that the user device is authorised to communicate with the alarm unit , in order to avoid tampering with the alarm units by unauthorised devices . As an example , the controller may be configured to trigger the test mode only if the control signal contains an authentication key that is recognised by the controller . The controller may be programmed to recognise one or more authentication keys . The controller may be configured to determine a test parameter of the test mode based on the received control signal , and to apply the determined test parameter when triggering the test mode . In this manner, parameters of the test mode may be set via the user device , which may greatly facilitate performing a desired test of the alarm unit . Parameters of the test mode may correspond to parameters of the alarm unit that are used during the test mode , and may comprise one or more of a duration of the test mode , a tone of the alarm, a volume of the alarm, and/or a flashing mode of a light source of the alarm unit .

The received control signal may include information indicative of one or more test parameters . For example , the user device may comprise a user interface for selecting one or more test parameters . Then, the user device may generate the control signal based on one or more test parameters selected by a user via the user interface .

The wireless communication interface of each alarm unit may be configured to receive alarm generation data from the user device , and the alarm unit may be configured to generate an alarm based on the received alarm generation data . In this manner , alarm generation data may be transmitted from the user device to the alarm unit , such that the alarm generated by the alarm unit is in accordance with the received alarm generation data . This may facilitate configuring the alarm unit with a desired alarm ( or 'alarm tone' ) . For example , the user device may be configured to store alarm generation data for a plurality of pre-set alarms . The user device may then be configured to , in response to selection of one of the pre-set alarms ( e . g . by a user via a user interface on the user device ) , transmit alarm generation data corresponding to the selected pre-set alarm to the alarm unit . This may also enable the user to configure the alarm unit with a custom alarm. For example , the user device may be configured to generate alarm generation data for a custom alarm, based on an input received from the user at the user device . The user input may indicate ( e . g . via a user interface on the user device ) one or more parameters for the custom alarm.

Wirelessly receiving alarm generation data at the alarm unit may avoid having to pre-configure each alarm unit with a series of pre-set alarms , as each alarm unit can be wirelessly configured on the fly to generate a desired alarm. In other words , only alarm generation data corresponding to the desired alarm need be transmitted and stored at the alarm unit . Thus , there may be no need to store alarm generation data for a plurality of pre-set alarms in each alarm unit , such that memory requirements for each alarm unit may be reduced . Instead, as mentioned above , alarm generation data for the plurality of pre-set alarms can be stored remotely in the user device .

The alarm generation data may include data indicative of one or more alarm ( or 'alarm tone' ) parameters . Examples of alarm parameters include tone type ( e . g . continuous , intermittent , alternating, sweeping ) , frequency parameters , temporal pattern of tone , and/or any other suitable parameters . The alarm unit may be configured to generate an alarm based on the one or more alarm parameters in the received alarm generation data , i . e . such that the alarm has properties corresponding to the one or more alarm parameters .

The alarm unit may be configured to store the received alarm generation data in a memory of the alarm unit . The alarm unit may then be configured to access the stored alarm generation data in order to generate the alarm .

In some cases , the alarm generation data may be included in the control signal received from the user device . Then, the alarm unit may be configured to trigger the test mode in response to receipt of the control signal , such that in the test mode the alarm unit generates an alarm in accordance with the received alarm generation data . In this manner, a user may at the same time set and test an alarm tone of the alarm unit . For each of the alarm units , the wireless communication interface may be configured to harvest energy from the control signal , in order to power the controller . Thus , when a control signal is received at the wireless communication interface , the controller may be powered such that it can trigger the test mode of the alarm unit . When no control signal is received, the controller may remain unpowered, such that it does not consume any power . This may avoid having to provide power continuously to the controller in the alarm unit , which may improve an overall energy efficiency of the alarm system . As an example , the control signal may be a radiofrequency ( RF) signal , and the wireless communication interface may comprise an NFC or a Bluetooth ® interface which is configured to harvest energy from the RF control signal to power the controller .

For each of the plurality of alarm units , the wireless communication interface may be further configured to receive a programming signal transmitted by a user device , and the controller may be configured to set an alarm generation parameter of the alarm unit based on the received programming signal . Thus , in addition to wirelessly triggering a test mode of an alarm unit , alarm generation parameters of the alarm unit may also be set via wireless communication with the alarm unit . As discussed above , this avoids having to use mechanical switches in the alarm units for setting parameters , such that integrity of the alarm units need not be compromised to set the alarm generation parameters . An alarm generation parameter for an alarm unit may comprise a tone of the alarm, a volume of the alarm, a flashing mode of a light source of the alarm unit , a display setting of a display of the alarm unit , or any other parameters relating to properties of the alarm generated by the alarm unit . The programming signal may include information indicative of an alarm generation parameter to be used by the alarm unit . While the test mode of an alarm unit is activated, the wireless communication interface may further be configured to receive a programming signal from the user device , and the controller of the alarm unit may be configured to adj ust an alarm generation parameter of the alarm unit based on the received programming signal . In this manner, the alarm generation parameter may be adj usted in real-time during the test mode , such that the alarm generated by the alarm unit changes during the test mode in accordance with the adj ustment to the alarm generation parameter . This may facilitate adj usting the alarm generation parameter to a desired setting , and ensuring that the alarm unit works correctly with the desired setting . Thus , the test mode of the alarm unit may effectively be used as a ' setup mode ' , during which alarm generation parameters of the alarm unit can be set . The programming signal received during the test mode may be similar to the programming signal discussed above .

The user device may comprise a user interface configured to receive a user input indicative of one or more alarm generation parameters for the alarm unit . Then, the user device may be configured to transmit a programming signal to the alarm unit based on a user input received via the user interface , i . e . the programming signal may contain information indicative of one or more alarm generation parameters selected via the user interface .

In embodiments where the alarm system comprises the user device , the user device may be configured to transmit the control signal to one of the plurality of alarm units and, following transmission of the control signal , capture a recording of the test mode of the alarm unit . In this manner, a recording of the test mode of the alarm unit may be automatically recorded by the user device . This may facilitate recording the results of tests on the alarm units . This may enable the recording of the test modes to be reviewed at a later date , e . g . for quality control . Such a recording of the test mode may form part of the test data discussed above . The recording may include an audio and/or video recording of the test mode . For example , the user device may comprise a microphone for capturing an audio recording of the test mode , and/or the user device may comprise a camera for capturing a video of the test mode . The recording of the test mode may be stored in a memory of the user device . Where the alarm system comprises a remote server, the user device may upload the recording of the test mode to the remote server .

For each of the plurality of alarm units , the controller may be configured to trigger the test mode by operating a power control switch in that alarm unit . This may enable , for example , the controller to control power delivered to an alarm generation module of the alarm unit . Thus , to trigger the test mode , the controller may operate the power control switch such that power is supplied to the alarm generation module , to cause the alarm generation module to generate an alarm . Then, once the test is completed ( e . g . after a predetermined amount of time ) , the controller may operate the power control switch such that power is no longer supplied to the alarm generation module .

The alarm system may be operable in an alarm mode in which each of the plurality of alarm units is arranged to generate an alarm, and a quiescent mode in which each of the plurality of alarm units is arranged to only generate an alarm when the test mode is triggered; and when the alarm system is in the quiescent mode and a control signal is received at the wireless communication interface of one of the plurality of alarm units , the controller of that alarm unit may be configured to trigger the test mode . Thus , under normal conditions , the alarm system may be in the quiescent mode , in which no alarm is generated . The alarm mode may be activated following detection of a predetermined condition ( e . g . outbreak of a fire ) , as discussed above . The control panel may be configured to control switching of the alarm system between the quiescent mode and the alarm mode . By enabling the test mode of an individual alarm unit to be triggered whilst the alarm system as a whole is in the quiescent mode , it is possible to test the alarm unit without triggering the alarm mode for the whole alarm system .

The alarm system may further comprise a first power line and a second power line coupled to each of the plurality of alarm units in order to deliver power to the plurality of alarm units and, in the quiescent mode , the control panel may configured to monitor integrity of the first and second power lines . In this manner , the control panel may detect if a fault arises on the power lines , which could compromise power supply to the alarm units . This may serve to improve a reliability of the alarm system. Various methods may be used for monitoring integrity of the power lines , some of which are discussed below .

The first power line and the second power line may couple the plurality of alarm units to a power supply . As noted above , the power supply may either be part of the control panel , or separate from the control panel . The plurality of alarm units may be connected in parallel to the first power line and second power line .

In the alarm mode , the control panel may be configured to establish a potential difference having a first polarity between the first power line and the second power line , which causes each of the plurality of alarm units to generate an alarm; and in the quiescent mode , the control panel may be configured to establish a potential difference between the first power line and the second power line having a second polarity, opposite to the first polarity, wherein the potential difference having the second polarity does not cause the alarm units to generate an alarm. Thus , the polarity between the first and second power lines is reversed in the quiescent mode compared to the alarm mode . The reversed polarity established between the first and second power lines in the quiescent mode avoids generation of an alarm by the alarm units , whilst enabling the control panel to continuously monitor integrity ( e . g . continuity) of the first and second power lines . For example , the control panel may be configured to monitor integrity of the first and second power lines by monitoring a property ( e . g . an impedance ) of the first and second power lines whilst in the quiescent mode . Such continuous monitoring of the power lines may be referred to as continuous reverse polarity monitoring .

As an example , the potential difference having the first polarity may be established between the first power line and the second power line by applying a positive voltage to the first power line and a negative voltage to the second power line ( or vice versa ) . Then, the potential difference having the second polarity may be established between the first power line and the second power line by applying a negative voltage to the first power line and a positive voltage to the second power line ( or vice versa ) . Thus , the control panel may invert the voltages applied to the first and second power lines when switching between the quiescent mode and the alarm mode .

Various methods may be used for configuring the alarm units such that the potential difference having the second polarity does not cause generation of an alarm . For example , each alarm unit may comprise a circuit which is configured to block power supply to the alarm generation module of the alarm unit when the potential difference having the second polarity is established between the first and second power lines , and to allow power supply to the alarm generation module when the potential difference having the first polarity is established between the first and second power lines . For instance , each alarm unit may comprise one or more diodes arranged to block power supply to the alarm generation module of the alarm unit in the quiescent mode , and to allow power supply to the alarm generation module in the alarm mode . Then, to trigger the test mode , the controller may operate a component of the circuit ( e . g . such as the power control switch mentioned above ) , so that power supply to the alarm generation module is temporarily enabled .

However , in some alarm systems , the control panel may not necessarily be configured to reverse the polarity between the first and second power lines in order to monitor integrity of the first and second power lines . For example , in some embodiments , when the alarm system is in the quiescent mode , no potential difference is established between the first and second power lines , i . e . there may be no voltage applied to the first and second power lines . Then, the control panel may monitor integrity of the first and second power lines by transmitting a pulsed voltage along the first and second transmission lines . The pulsed voltage may have a sufficiently short duration and small amplitude such that it does not cause the alarm units to generate an alarm, however it may be sufficient to enable detection of a fault on the power lines .

In such an embodiment , the alarm system may further comprise a switching module to enable switching of the polarity across the first and second power lines . Thus , in some embodiments , in the alarm mode , the control panel may be configured to establish a potential difference having a first polarity between the first power line and the second power line , which causes each of the plurality of alarm units to generate an alarm; and the alarm system may further comprise a switching module that is operable to switch the polarity of the potential difference between the first power line and the second power line to a second polarity, opposite to the first polarity, wherein the potential difference having the second polarity does not cause the alarm units to generate an alarm. Then, in order to trigger the test mode of an alarm unit in such an embodiment , the control panel may be operated in order to trigger the alarm mode , and the switching module may be operated to switch the polarity of the potential difference between the first and second power lines to the second polarity . In this configuration, no alarm is generated by the alarm units , due to the reversed polarity across the power lines . The test mode of an individual alarm unit may then be triggered in a similar manner to that discussed above .

The switching module may be connected between the control panel and the first and second power lines . The switching module may be manually operable , and may require a key to operate , in order to improve security .

For each of the plurality of alarm units , when the alarm system is in the quiescent mode , the controller may be powered via the first and second power lines . This may avoid having to harvest energy from the control signal , in order to power the controller , which may simplify the electronics of the wireless communication interface . The controller may be arranged to only draw a small amount of current from the power lines ( e . g . of the order of 100 pA) , such that it does not affect any power line monitoring performed by the control panel . As an example , the controller may be coupled to the first and second power lines via a large resistance resistor ( e . g . a "bleed resistor" ) , such that it only draws a small current .

Each individual alarm unit of the alarm system discussed above may be considered as an independent aspect of the invention . Thus , according to a second aspect of the invention, there is provided an alarm unit for an alarm system, the alarm unit comprising : a wireless interface communication interface configured to receive a control signal transmitted by a user device ; and a controller configured to trigger a test mode of the alarm unit in response to receipt of the control signal . The alarm unit of the second aspect of the invention may include any features discussed above in relation to the alarm units of the first aspect of the invention .

According to a third aspect of the invention, there is provided an alarm system comprising : a plurality of alarm units , each alarm unit being configured to generate an alarm; and a control panel configured to control power supplied to the plurality of alarm units ; wherein each of the plurality of alarm units comprises a wireless communication interface for receiving a programming signal transmitted by a user device , and a controller configured to set an alarm generation parameter of the alarm unit based on the received programming signal . Thus , the alarm system of the third aspect of the invention enables wireless setting of alarm generation signals for individual alarm units of the system . The alarm system of the third aspect of the invention may further include any of the features discussed above in relation to the first aspect of the invention . In some embodiments , in response to receipt of the programming signal from the user device , the controller may be configured to authenticate the user device prior to setting the alarm generation parameter of the alarm unit .

The programming signal may include alarm generation data, as discussed above in relation to the first aspect of the invention . The alarm generation data may include data indicative of one or more alarm generation parameters . The alarm unit may be configured to store the alarm generation data in a memory of the alarm unit .

In response to receiving the programming signal , the controller of the alarm unit may be configured to set the alarm generation parameters of the alarm unit in accordance with the alarm generation parameters included in the programming signal . In this manner , when a test mode or an alarm mode is triggered, the alarm unit will generate an alarm in accordance with the alarm generation data included in the programming signal . Thus , the controller may be configured to , in response to an alarm mode of the alarm system being triggered, generate an alarm in accordance with the alarm generation data included in the programming signal .

Each individual alarm unit of the alarm system of the third aspect of the invention may be considered as an independent aspect of the invention . Thus , according to a fourth aspect of the invention, there is provided an alarm unit for an alarm system, the alarm unit comprising : a wireless communication interface for receiving a programming signal transmitted by a user device ; and a controller configured to set an alarm generation parameter of the alarm unit based on the received programming signal . The alarm unit of this aspect may include any features discussed above in relation to the alarm units of the first aspect of the invention .

According to a fifth aspect of the invention, there is provided a method of operating an alarm system . The method of this aspect may be used to operate the alarm system of the first aspect of the invention . Therefore , any features discussed above in relation to the first aspect of the invention may be shared with the method of this aspect .

According to the fifth aspect of the invention, there is provided a method of operating an alarm system comprising a plurality of alarm units , each alarm unit being configured to generate an alarm, and a control panel configured to control power supplied to the plurality of alarm units , wherein the method comprises : receiving, via a wireless communication interface in one of the plurality of alarm units , a control signal transmitted by a user device ; and triggering , by a controller of the alarm unit , a test mode of the alarm unit .

The test mode may comprise generating an alarm by the alarm unit .

The method may comprise storing a respective identifier in each of the alarm units .

The method may comprise recording test data relating to instances when the test mode of any of the plurality of alarm units was triggered .

The method may comprise storing, in each of the plurality of alarm units , test data relating to instances when the test mode of that alarm unit was triggered . The method may comprise transmitting , via the wireless communication information of one of the alarm units , test data stored therein to a user device .

The method may comprise storing , in a remote server of the alarm system, test data relating to instances when the test mode of any of the plurality of alarm units was triggered .

The method may comprise , in response to receipt of the control signal from the user device , authenticating, by the controller, the user device prior to triggering the test mode of the alarm unit .

The method may comprise : determining, by the controller, a test parameter of the test mode based on the received control signal ; and applying the determined test parameter when triggering the test mode .

The method may comprise : receiving , by the wireless communication interface of the alarm unit , alarm generation data from the user device , and generating , by the alarm unit , an alarm based on the received alarm generation data .

The method may comprise harvesting , by the wireless communication interface of the alarm unit , energy from the control signal in order to power the controller .

The method may comprise : receiving , by the wireless communication interface , a programming signal transmitted by the user device ; and setting, by the controller , an alarm generation parameter of the alarm unit based on the received programming signal .

The method may comprise transmitting , by the user device , the control signal to one of the plurality of alarm units and, following transmission of the control signal , capturing with the user device a recording of the test mode of the alarm unit .

The method may comprise triggering the test mode of an alarm unit by operating a power control switch in that alarm unit . The alarm system may be operable in an alarm mode in which each of the plurality of alarm units is arranged to generate an alarm, and a quiescent mode in which each of the plurality of alarm units is arranged to only generate an alarm when the test mode is triggered; and the method may further comprise , when the alarm system is in the quiescent mode and a control signal is received at the wireless communication interface of one of the plurality of alarm units , triggering the test mode by the controller .

The alarm system may further comprise a first power line and a second power line coupled to each of the plurality of alarm units in order to deliver power to the plurality of alarm units , and the method may further comprise , in the quiescent mode , monitoring integrity of the first and second power lines .

The method may comprise , in the alarm mode , the establishing of a potential difference having a first polarity between the first power line and the second power line , which causes each of the plurality of alarm units to generate an alarm; and in the quiescent mode , establishing a potential difference between the first power line and the second power line having a second polarity, opposite to the first polarity, wherein the potential difference having the second polarity does not cause the alarm units to generate an alarm .

The method may comprise , in the alarm mode , establishing a potential difference having a first polarity between the first power line and the second power line , which causes each of the plurality of alarm units to generate an alarm; and operating a switching module to switch a polarity of the potential difference between the first power line and the second power line to a second polarity, opposite to the first polarity, wherein the potential difference having the second polarity does not cause the alarm units to generate an alarm . The method may comprise , when the alarm system is in the quiescent mode , powering the controller via the first and second power lines .

According to a sixth aspect of the invention, there is provided a method of operating an alarm system comprising a plurality of alarm units , each alarm unit being configured to generate an alarm, and a control panel configured to control power supplied to the plurality of alarm units , wherein the method comprises : receiving, via a wireless communication interface in one of the plurality of alarm units , a programming signal transmitted by a user device ; and setting, by the controller, an alarm generation parameter of the alarm unit based on the received programming signal . The method of this aspect may be used to operate the alarm system of the third aspect of the invention . Any features discussed above in relation to previous aspects may be shared with this aspect of the invention .

BRIEF DESCRIPTION OF THE DRAWINGS

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

Fig . 1 is a schematic diagram of an alarm system that is an embodiment of the invention;

Fig . 2 is a schematic diagram of an alarm system that is an embodiment of the invention;

Fig . 3 is a schematic diagram of an alarm system that is an embodiment of the invention; and

Fig . 4 is a schematic diagram of an alarm system that is an embodiment of the invention .

DETAILED DESCRIPTION; FURTHER OPTIONS AND PREFERENCES Fig . 1 is a schematic diagram of an alarm system 100 according to an embodiment of the invention . The alarm system includes a plurality of alarm units 102a-c, each of which is configured to generate an alarm. For example , each of the alarm units 102a-c may comprise a sounder for generating an audible alarm, and/or a light source or display for generating a visual alarm . The alarm units 102a-c may be mounted at different locations across a site , e . g . at different locations in a building . In the example shown, the alarm system 100 has three alarm units 102a-c , however in practice there may be any number of alarm units .

The alarm system 100 further comprises a control panel 104 , which is configured to control power supplied to the alarm units 102a-c . In the example shown, the control panel 104 includes a power supply unit 106 , which is coupled to each of the alarm units 102a-c via a first power line 108 and a second power line 110 . The alarm units 102a-c are connected to the power lines 108 , 110 in parallel , so that they can each receive power from the power supply unit 106 in the control panel 104 . The control panel 104 further comprises a controller 112 which is coupled to the power supply unit 106 and configured to control power delivered to the alarm units 102a-c by the power supply unit 106 . The controller 112 may be in the form of an internal computing device , a microcontroller , or other suitable processing unit for controlling the power supply unit 106 . It should be noted that , in other examples ( not shown ) , the power supply unit 106 may be external to the control panel 104 , i . e . the power supply unit 106 is not necessarily integrated with the control panel 104 . In such an example , the control panel 104 may be configured to transmit control signals from the controller 112 to the external power supply unit via a suitable communication channel ( e . g . via a wired or wireless connection) . In some cases , the alarm system 100 may comprise multiple power supply units , e . g . where the system includes a large number of alarm units that are spread out over a large area . In such a case , the control panel 104 may be configured to control power supplied by each of the power supply units .

The alarm system 100 may further comprise an end of line ( EOL ) device 114 connected between distal ends of the first and second power lines 108 , 110 . The EOL device 114 may, for example , be a resistor connected between distal ends of the first and second power lines 108 , 110 . The EOL device 114 may enable the control panel to verify integrity of the first and second power lines 108 , 110 , e . g . to ensure that there are no discontinuities in the power lines which could prevent any of the alarm units 102a-c from generating an alarm. The control panel 104 may be configured to monitor integrity of the first and second power lines 108 , 110 , by detecting a resistance of the first and second power lines 108 , 110 and the EOL device 114 , e . g . by establishing a voltage across the EOL device 114 and/or by transmitting a pulsed voltage along the first and second power lines 108 , 110 .

The control panel 104 may be configured to switch the alarm system 100 between a quiescent mode , in which the alarm units 102a-c do not generate an alarm, and an alarm mode in which each of the alarm units 102a-c generates an alarm . The control panel 104 may trigger the alarm mode in response to the system detecting that a predetermined condition is met . For example , the alarm system 100 may further comprise one or more detectors ( not shown) which are communicatively coupled to the controller 112 . Then, based on detection signals received from the detectors , the controller 112 may determine that a predetermined condition has been met and that the alarm mode should be triggered . The controller 112 triggers the alarm mode by controlling the power supply unit 106 in order to cause the alarm units 102a-c to generate an alarm . As an example , where the alarm system 100 is a fire alarm system, the alarm system 100 may include one or more smoke detectors . Of course , different types of detectors may be used depending on the intended purpose of the system. The alarm system 100 may also include one or more switches disposed across the site to enable a person to manually trigger the alarm mode .

In some embodiments , the alarm system 100 may also include a pre-alarm mode , which may be activated by the control panel 104 prior to triggering the full alarm mode . The pre-alarm mode may act as an advance warning that the alarm mode may soon be triggered . For example , whilst in the prealarm mode , one or more of the alarm units 120a-c may generate a pre-alarm, which may include an audible alarm ( e . g . which may have a lower volume than the alarm generated in the alarm mode ) and/or a visual alarm ( e . g . one or more warning lights on the alarm units may be activated) . In such an embodiment , the alarm system 100 may include a third power line ( not shown ) , which connects the power supply unit 106 to each of the alarm units 102a-c . Then, when the pre-alarm mode is activated, power may be supplied to the alarm units 102a-c via the first power line 108 and the third power line , in order to cause generation of the pre-alarm by the alarm units 102a-c . To switch to the alarm mode , the control panel 104 may then switch from the third power line to the second power line 110 , such that power is supplied to the alarm units 102a-c via the first and second power lines 108 , 110 , which causes generation of the full alarm .

Each of the alarm units 102a-c is configured to communicate wirelessly with a user device 116 . More specifically, each alarm unit comprises a wireless communication interface for receiving wireless signals from, and transmitting wireless signals to , the user device 116 . Each alarm unit also includes a controller ( e . g . a microcontroller ) , which is configured to control operation of the alarm unit based on signals received from the user device 116 . In this manner , a user way control each of the alarm units 102a-c via the user device 116 . The user device 116 may, for example , be a smartphone or other portable computing device having suitable software installed thereon for communicating with the alarm units 102a-c , or the user device 116 may be a remote control that is designed specifically for use with the alarm system 100 . The user device 116 may have a user interface , which enables a user to transmit various instructions wirelessly to an alarm unit .

Wireless communication between the user device 116 and each of the alarm units 102a-c may take any suitable form of wireless communication . In some cases , the user device 116 may be configured to communicate with the alarm units 102a-c via radiofrequency ( RF) signals , in which case the wireless communication interfaces in the alarm units 102a-c may comprise RF antennas . For example , communication between the user device 116 and each of the alarm units 102a-c may be based on near-field-communication (NFC ) technology, or Bluetooth ® technology . In other cases , the user device 116 may be configured to communicate with the alarm units 102a-c via light ( e . g . infrared ) signals , in which case the wireless communication interfaces in the alarm units 102a-c may comprise a photodetector . In yet further cases , the user device 116 may be configured to communicate with the alarm units 102a-c via sound ( e . g . ultrasound ) signals , in which case the wireless communication interfaces in the alarm units 102a-c may comprise a sound detector ( e . g . a microphone ) .

In one embodiment , the user device 116 is configured to transmit a control signal to one of the alarm units 102a-c, in order to cause that alarm unit to enter a test mode . Upon receipt of the control signal at the wireless communication interface of one of the alarm units 102a-c, the controller of that alarm unit triggers the test mode of the alarm unit . The test mode of the alarm unit may include generating an alarm by that alarm unit , so that proper functioning of the alarm unit can be verified .

For instance , in the example shown in Fig . 1 , the user device 116 transmits a wireless control signal 118 to alarm unit 102a which, upon receipt of the control signal 118 , enters the test mode . The control signal 118 may for example contain an instruction for the alarm unit 102a to enter the test mode . The control signal 118 may also contain one or more test parameters that are to be used by the alarm unit in the test mode . Test parameters may include various settings of the alarm unit 102a , such as its tone setting, volume setting, light flashing settings , and/or display settings . The test parameters can also include a duration for which the test mode is to be triggered . Upon receipt of the control signal , the controller of the alarm unit 102a can determine one or more test parameters based on the information in the control signal , and then apply the determined test parameters during the test mode . In this manner, particular settings of the alarm unit 102a can be tested .

Each of the alarm units 102a-c may include an internal memory ( e . g . a non-volatile memory) which stores a unique identifier for that alarm unit . The unique identifier may for an alarm unit , for example , be a number, code or name which uniquely identifies that alarm unit from the other alarm units in the system. This may facilitate keeping a record of tests that are performed on individual alarm units , as well as enable the user device 116 to identify the different alarm units . For instance , the user device may transmit a query to one of the alarm units 102a-c , which then responds with an indication of its unique identifier . In some cases , the unique identifier of an alarm unit may correspond to an identifier of its wireless communication interface , e . g . such as an NFC identifier . Each of the alarm units 102a-c may also be configured to store information relating to a company or an engineer that installed the system or is responsible for maintaining and testing the system 100 .

The alarm system 100 is configured to record test data relating to instances when the test mode of any of the alarm units 102a-c was triggered . In other words , the system may maintain a log of tests performed on each of the alarm units 102a-c . The test data can include , for example , a date and/or time when the test mode of the alarm unit was triggered, an identifier of the user device 116 that triggered the test mode , a duration for which the test mode was triggered, one or more settings of the alarm unit during the test mode ( e . g . alarm tone , volume , etc . ) , or any other relevant information .

The alarm system 100 includes a remote server 120 , where all of the test data for the system 100 is stored in a database . The remote server 120 may be a cloud server, which is connected to the internet 122 . In this manner , the user device 116 may communicate wirelessly with the remote server 120 via the internet 122 . Following transmission of a control signal by the user device 116 to one of the alarm units 102a-c to trigger the test mode in that alarm unit , the user device may transmit corresponding test data to the remote server 120 , which may then store the received test data in its database . The test data transmitted by the user device 116 may include the unique identifier of the alarm unit in which the test mode was triggered . In this manner, the remote server 120 can associate the received test data with the relevant alarm unit in its database . Accordingly, each time the user device 116 triggers a test mode in one of the alarm units 102a-c , test data may be automatically uploaded to the remote server 120 . Additionally to transmitting the test data , the user device 116 may also be configured to store a copy of the test data in a memory of the user device 116 . The test data stored on the user device 116 may then be viewed via an application running on the user device 116 .

The test data transmitted by the user device 116 may also include an indication of a result or outcome of the test mode that was triggered in the alarm unit . For example , the test data may indicate whether the alarm unit successfully generated an alarm when the test mode was triggered, or whether a fault with the alarm unit was detected . The user device 116 may provide a user interface which enables a user to input the result of the test mode , so that the result can be recorded . Additionally or alternatively, the user device 116 may be configured to capture a recording of the test mode . The user device 116 may include a microphone and/or camera to enable capturing of an audio and/or video recording of the test mode . Then, after transmitting a control signal to one of the alarm units 102a-c to trigger the test mode of the alarm unit , the user device 116 may automatically capture a recording of the test mode of the alarm unit . The recording may be uploaded to the remote server 120 as part of the test data .

The database of test data stored by the remote server 120 may be accessed via a computer 124 ( or any other computing device ) that is connected to the remote server 120 via the internet 122 . For example , the remote server 120 may be configured to generate an interface for viewing the database of test data e . g . via a web browser on the computer 124 . The remote server 120 may also store further information relating to the alarm system 100 . For example , the remote server 120 may store information relating to a company or engineer that installed the alarm system 100 or is responsible for maintaining and testing the system 100 .

Test data may also be stored directly within the alarm units 102a-c themselves , e . g . each alarm unit may comprise a memory ( e . g . non-volatile memory for storing test data ) . In particular, the controller of an alarm unit may be configured to , following the triggering of the test mode , record test data relating to the triggering of the test mode in the memory of the alarm unit . As a result , each alarm unit may maintain a record of tests performed on that alarm unit . The user device 116 may then be able to retrieve the test data stored on an alarm unit , e . g . by transmitting an appropriate query to the alarm unit . In response to receiving such a query, the alarm unit may transmit a reply signal to the user device 116 which contains information indicative of the test data stored therein .

Additionally or alternatively to the ability to trigger testing of the alarm units 102a-c wirelessly, wireless communication with the alarm units 102a may be used to set or modify various settings of the alarm units 102a-c . In particular, wireless communication of the user device 116 with the alarm units 102a-c may be used to set alarm generation parameters of the alarm units . An alarm generation parameter of an alarm unit may, for example , comprise a tone of the alarm, a volume of the alarm, a flashing mode of a light source of the alarm unit , or any other parameters relating to properties of the alarm generated by the alarm unit . Each alarm unit may have one or more alarm generation parameters stored in a memory therein, such that the alarm unit is configured to generate an alarm in accordance with the stored alarm generation parameters . In other words , when the test mode of the alarm unit is triggered, or when the alarm mode of the alarm system 100 is triggered, the alarm unit may generate an alarm in accordance with the stored alarm generation parameters .

Thus , in one embodiment , user device 116 is configured to transmit a programming signal to one of the alarm units 102a- c , in order to set an alarm generation parameter of that alarm unit . Upon receipt of the programming signal at the wireless communication interface of one of the alarm units 102a-c, the controller of that alarm unit is configured to set an alarm generation parameter of the alarm unit based on the received programming signal . In particular, the controller of the alarm unit may update the alarm generation parameters stored in the alarm unit ' s memory, based on the alarm generation parameters contained in the programming signal . For example , the programming signal may contain an indication of an alarm tone to be used by the alarm unit , and/or an alarm volume to be used by the alarm unit . In some cases, after the user device 116 transmits a control signal to one of the alarm units 102a-c to trigger the test mode of that alarm unit, the user device 116 may further transmit a programming signal to that alarm unit. In this manner, an alarm generation parameter of the alarm unit may be adjusted whilst the test mode is activated. This may enable an engineer to adjust an alarm generation parameter (such as alarm volume or tone) in real-time during the test mode. More specifically, after the test mode is triggered in one of the alarm units 102a-c, and whilst the test mode is still active, the wireless communication interface of that alarm unit may receive a programming signal from the user device 116. Then, the controller of that alarm unit may adjust an alarm generation parameter based on the received programming signal (e.g. using an indication of an alarm generation parameter contained in the programming signal) . As a result, the alarm generated by the alarm unit during the test mode may change in accordance with the adjustment to the alarm generation parameter. For instance, where the programming signal includes an indication that alarm volume should be adjusted (e.g. increased or decreased) , the volume of the alarm generated by the alarm unit may increase or decrease accordingly.

The programming signal may include alarm generation data which is indicative of one or more alarm generation parameters for the alarm units 102a-c. In one embodiment, the alarm generation parameters may correspond to parameters of an alarm tone (i.e. an audible alarm) generated by the alarm unit. For example, the one or more parameters may be indicative of an alarm tone type. Possible alarm tone types include a continuous tone (e.g. where sound is continuously emitted by the alarm unit) , an intermittent tone (e.g. the alarm unit emits sound intermittently) , an alternating tone (e.g. where the alarm unit alternates between sounds at different frequencies) , a sweeping tone (e.g. where the alarm unit emits a sound that sweeps from a first frequency to a second frequency) , or any other suitable type of alarm tone . The one or more parameters may also include frequency parameters , e . g . to indicate a frequency ( or frequencies ) of sound emitted by the alarm unit . For instance , where the alarm tone is continuous or intermittent , the one or more parameters may indicate a frequency of the sound emitted by the alarm unit . Where the alarm tone is sweeping , the one or more parameters may indicate a starting frequency and an ending frequency for the sweeping alarm tone . Where the alarm tone is alternating, the one or more parameters may indicate two or more frequencies between which the alarm unit alternates when generating the alarm tone . The one or more parameters may also be indicative of a temporal pattern of the alarm tone . For example , the one or more parameters may be indicative of a duration of the alarm tone , a repetition rate of the alarm tone , a duration of any pauses between alarm tones , and/or any other parameters relating to timing of the alarm tones . Thus , the one or more parameters included in the alarm generation data may fully characterise the alarm tone to be generated by the alarm unit , and specify any parameters needed by the alarm unit for generating the alarm tone .

The user device 116 may be authenticated by the alarm system 100 , to ensure that the user device 116 is authorised to control the alarm units 102a-c . This may be achieved by registering the user device 116 with a registration service . For example , an application on the user device 116 that is used to communicate with the alarm units 102a-c may require the user to register with the registration service , in order to authorise use of the user device 116 with the alarm system 100 . The registration service may be an online registration service , which is run via remote server 120 , or via another cloud server . Following authorisation of the user device 116 , the user device 116 may receive one or more authentication keys from the registration service , and which are used when communicating with the alarm units 102a-c . Then, when transmitting a signal ( e . g . a control signal , or programming signal , or a query) to one of the alarm units 102a-c, the user device 116 may include an authentication key in the signal , so that the alarm unit can authenticate the user device 116 . Each alarm unit may be configured to recognise one or more specific authentication keys , such that it does not respond to a signal which does not contain a recognised authentication key . Thus , for example , an alarm unit may only trigger its test mode in response to receiving a control signal if the control signal contains an authentication key that is recognised by that alarm unit . Similarly, an alarm unit may only update its alarm generation parameters based on a received programming signal if the programming signal contains a recognised authentication key . Each of the alarm units 102a-c may be registered with the registration service , and the registration service may store authentication keys for each of the alarm units 102a-c . In this manner, the registration service can provide the user device 116 with authentication keys that are specific to the alarm units 102a-c with which the user device 116 is intended to interact with .

Fig . 2 is a schematic diagram of an alarm system 200 according to an embodiment of the invention . The alarm system 200 comprises an alarm unit 202 which is coupled to a control panel 204 via a first power line 206 and a second power line 208 . The alarm unit 202 may, for example , correspond to one of the alarm units 102a-c discussed above , whilst control panel 204 may correspond to control panel 104 discussed above . In particular, the control panel 204 is configured to control power supplied to the alarm unit 202 via the first and second power lines 206 , 208 . The alarm system 200 may comprise further alarm units coupled to the first and second power lines 206 , 208 ( e . g . in parallel with alarm unit 202 ) , however for illustration purposes only a single alarm unit is depicted in Fig . 2 . The alarm unit 202 comprises an alarm generation module 210, which is configured to generate an alarm when it receives power, e.g. when a current passes through it. For instance, the alarm generation module 210 may comprise a sounder (e.g. speaker) for generating an audible alarm, and/or a light source or display for generating a visual alarm. A first voltage input 212 of the alarm generation module 210 is coupled to the first power line 206 via a first diode 214, and to the second power line 208 via a second diode 216, the first and second diodes being arranged to only transmit a positive voltage to the first input 212. A second voltage input 218 of the alarm generation module is connected to a power control switch 220. The power control switch 220 is controllable via a signal input 222, and is switchable between an open state and a closed state. When no voltage or a negative voltage is applied to the signal input 222, the power control switch 220 is in the open stage; when a positive voltage is applied to the signal input 222, the power control switch 220 is in a closed state. The power control switch 220 is configured such that, when it is in the closed state, it connects the second voltage input 218 to ground 224; when the power control switch 220 is in the open state, the second voltage input 218 is isolated. The power control switch 220 may, for example, be a metal-oxide-semiconductor field-effect transistor (MOSFET) , whose gate is connected to the signal input, whose source is connected to the ground 224, and whose drain is connected to the second voltage input 218.

The alarm unit 202 further comprises a wireless communication interface 226, which is communicatively coupled to a controller 228 of the alarm unit 202. The wireless communication interface 226 is configured to receive wireless signals from a user device (e.g. user device 116) , and convey the received signals to the controller 228. In some cases, the wireless communication interface 226 may comprise a decoder, which is arranged to decode received signals and put them in a format that is suitable for the controller 228 . As an example , the wireless communication interface may comprise an NFC antenna and corresponding electronics . The controller 228 is connected to the signal input 222 of the power control switch 220 via a third diode 230 , the third diode being arranged to only transmit a positive voltage from the controller 228 to the signal input 222 .

The signal input 222 is further coupled to the first power line 206 via a resistor 232 . Additionally, as shown in Fig . 2 , the first power line 206 is coupled to ground via a fourth diode 234 , and the second power line 208 is coupled to ground via a fifth diode 236 . The fourth diode 234 is arranged to block a positive voltage from being transmitted from the first power line 206 to ground, and similarly the fifth diode 236 is arranged to block a positive voltage from being transmitted from the second power line 208 to ground . A sixth diode 233 is connected between the resistor 232 and the signal input 222 , the sixth diode being arranged to block a negative voltage from being transmitted from the first power line 206 to the signal input 222 via the resistor 232 .

The control panel 204 is configured to switch the alarm system 200 between a quiescent mode , in which the alarm unit 202 do not generate an alarm, and an alarm mode in which the alarm unit 202 generates an alarm . In the quiescent mode , the control panel 204 applies a negative voltage to the first power line 206 , and a positive voltage to the second power line 208 . In this configuration, no positive voltage is connected to the signal input 222 of the power control switch 220 remains in the open state , such that the second voltage input 218 of the alarm generation module 210 is not connected to ground 224 . Accordingly, the alarm generation module 210 is isolated from power supplied by the control panel 204 , and so does not generate an alarm .

As a potential difference is established between the first and second power lines 206 , 208 in the quiescent mode (due to the voltages applied thereto) , the control panel 204 can continuously monitor integrity of the first and second power lines 206, 208. For example, the alarm system 200 may include an EOL device (e.g. similar to EOL device 114) which is connected between distal ends of the first and second power lines 206, 208, such that the control panel 204 can monitor an impedance of the EOL device. This may enable the control panel to detect if and when a fault on one of the first and second power lines 206, 208 occurs.

When the alarm system 200 is in the quiescent mode, a test mode of the alarm unit 202 can be triggered by a user device (e.g. user device 116) transmitting a control signal to the wireless communication interface 226. Upon receipt of the control signal, the wireless communication interface 226 may be configured to harvest power from the control signal, in order to temporarily power the controller 228. For example, where the control signal is an RF signal (such as for near- field-communication) , the wireless communication interface 226 may include a power harvesting circuit configured to harvest power from the RF signal, and convey the harvested power to the controller 228. The harvested power may also serve to power the decoder used for decoding the received signal. Additionally or alternatively, the controller 228 may be powered via the first and second power lines 206, 208 when the alarm system 200 is in the quiescent mode. For example, the controller 228 may be coupled the first and second power lines 206, 208 via a bleed resistor, so that it may draw a minimal current from the power lines when in the quiescent mode. Such a method of powering the controller 228 may be particularly relevant, for example, where the wireless communication interface 226 is not configured to harvest energy from the control signal.

Following receipt of the control signal, the controller 228 activates the power control switch 220, by transmitting a signal to the signal input 222 via the third diode 230. This switches the power control switch 220 to the closed state , such that the second voltage input 218 is connected to the ground 224 . The negative voltage on the first power line 206 is coupled to the ground 224 via the fourth diode 234 , such that the negative voltage is applied to the second voltage input 218 . Likewise , the positive voltage on the second power line 208 is transmitted to the first voltage input 212 via the second diode 216 . Thus , in this state , power may be supplied to the alarm generation module 210 from the first and second power lines 206 , such that the alarm generation module 210 may generate an alarm . In this state , the controller 228 may no longer rely on power harvested via the wireless communication interface 226 , and may instead receive power from the first and second power lines 206 , 208 . In particular , as shown in Fig . 2 , the controller 228 may be connected to the alarm generation module 210 in order to receive power from the alarm generation module 210 . In some cases , the controller 228 may be integrated within the alarm generation module 210 . While in the test mode , the sixth diode 233 prevents the negative voltage on the first power line from reaching the signal input 222 .

The test mode may continue for a predetermined duration . The predetermined duration may be pre-programmed in the controller 228 , or it may be determined based on instructions included in the control signal . At the end of the predetermined duration, the controller 228 terminates the signal transmitted to the signal input 222 of the power control switch 220 , to cause the power control switch 220 to return to the open state . As a result of this , power to the alarm generation module 210 is cut off , such that it stops generating the alarm. The system is thus returned to the quiescent mode where no alarm is generated .

To switch from the quiescent mode to the alarm mode of the alarm system 200 , the control panel 204 switches the polarities of the voltages applied to the first and second power lines 206 , 208 . Specifically, the control panel 204 applies a positive voltage to the first power line 206 , and a negative voltage is applied to the second power line 208 . This results in a positive voltage being applied to the signal input 222 via the resistor 232 , which causes the power control switch 220 to switch to the closed state , thus coupling the second voltage input 218 to the ground 224 . The positive voltage on the first power line is also transmitted to the first voltage input 212 via the first diode 214 . The negative voltage on the second power line 208 is transmitted, via the fifth diode 236 , to the ground 224 and thus to the second voltage input 218 . According , the positive voltage is transmitted to the first voltage input 212 and the negative voltage is transmitted to the second voltage input 218 , such that power can be supplied to the alarm generation module 210 and the controller 228 , such that an alarm may be generated .

The controller 228 may be configured to control generation of the alarm by the alarm generation module 210 . In particular , the controller 228 may be configured to control parameters or properties of the alarm generated by the alarm generation module 210 . For instance , the controller 228 may control a tone or volume of the alarm, as well as any flashing or display settings of the alarm generation module 210 .

Where the alarm system 200 includes a pre-alarm mode , the alarm system 200 may further comprise a third power line ( not shown ) between the control panel 204 and the second voltage input 218 of the alarm generation module 210 , so that a negative voltage can be supplied to the second voltage input 218 via the third power line . Then, when the alarm system 200 is in the pre-alarm mode , a positive voltage may be supplied to the first voltage input 212 via the first power line 206 , and a negative voltage may be supplied to the second voltage input 218 via the third power line , such that the alarm generation module 210 is powered and can generate a pre-alarm . Of course , it will be appreciated that the circuit arrangement depicted in Fig . 2 is provided for illustrative purposes , and that in practice other circuit arrangements may be used to achieve similar effects .

Fig . 3 is a schematic diagram of an alarm system 300 according to an embodiment of the invention . The alarm system 300 comprises an alarm unit 302 that is coupled to a control panel 304 via a first power line 306 and a second power line 308 . The control panel 304 may be configured in a similar manner to control panels 104 and 204 discussed above . For illustration purposes , the alarm system 300 is shown as having only one alarm unit 302 ; however , in practice the alarm system 300 may include multiple alarm units which are connected in parallel to the first and second power lines 306 , 308 .

The alarm unit 302 comprises an alarm generation module 310 , which is configured to generate an alarm. The alarm generation module 310 may, for example , be similar to the alarm generation module 210 discussed above . The alarm generation module 310 may include a sounder for generating an audible alarm, and/or a light source or display for generating a visual alarm. Additionally, the alarm generation module 310 comprises a first controller 312 which is configured to control alarm generation by the alarm generation module 310 . For example , the first controller 312 may be configured to control alarm generation parameters of the alarm generation module 310 , such as alarm tone , alarm volume , flashing settings , and/or display settings . In some cases , the alarm generation module 310 may comprise a mechanical switch ( e . g . a DIL switch) , which is used for setting the alarm generation parameters of the alarm generation module 310 .

The alarm unit 302 further comprises a test module 314 , which is configured to control power supply to the alarm generation module 310 , as well as triggering of a test mode of the alarm unit 302 . The test module 314 is electrically connected at one end to the first and second power lines 306 , 308 , and at a second end to a first voltage input 316 and a second voltage input 318 of the alarm generation module 310 . The test module 314 includes a wireless communication interface 320 and a second controller 322 , which may function in a similar manner to the wireless communication interface 226 and the controller 228 discussed above , respectively .

The test module 314 is configured to not transmit any power from the first and second power lines 306 , 308 to the first and second voltage inputs 316 , 318 when the alarm system is in the quiescent mode ( e . g . when a negative voltage is applied to the first power line 306 and a positive voltage is applied to the second power line 308 ) , such that the alarm generation module 310 does not generate an alarm in the quiescent mode . Furthermore , the test module 314 is configured to transmit power from the first and second power lines 306 , 308 to the first and second voltage inputs 316 , 318 when the alarm system is in the alarm mode ( e . g . when a positive voltage is applied to the first power line 306 and a negative voltage is applied to the second power line 308 ) , such that the alarm generation module 310 generates an alarm in the alarm mode . The test module 314 is further configured to trigger a test mode when the alarm system is in the quiescent mode and a control signal from a user device is received at the wireless communication interface 320 , by causing power to be supplied from the first and second power lines 306 , 308 to the first and second voltage inputs 316 , 318 such that the alarm generation module 310 generates an alarm. Thus , the test module 314 may include circuitry similar to that described above in relation the alarm unit 202 for controlling power supply to the alarm generation unit 210 via the first and second voltage inputs 212 , 218 . In particular , the test module 314 may include a similar arrangement of diodes , power control switch, resistor , and ground connections as discussed above in relation to the alarm unit 202 . Thus , in the alarm unit 302 , all of the circuitry for controlling triggering of the test mode is self-contained within the test module 314 . Accordingly, the alarm generation module 310 need not include any of the electronics related to wireless communication with the alarm unit 302 , and may therefore comprise standard or conventional circuitry for an alarm generation module . The arrangement of the alarm generation unit 302 may therefore enable existing alarm generation modules to be retro-fitted with a test module 314 , to enable wireless testing of the alarm unit , without having to reconfigure the alarm generation module . This may be advantageous , as alarm generation modules typically need to undergo rigorous testing and certification procedures prior to be launched on the market . Retro-fitting existing alarm generation modules with a test module 314 may avoid having to repeat the ( often expensive ) testing and certification procedures for the alarm generation module . This may also facilitate upgrading existing alarm systems to provide them with wireless capabilities . The alarm unit 302 may comprise a single housing in which the alarm generation module 310 and test module 314 are disposed, e . g . as indicated by the dashed line in Fig . 3 .

Fig . 4 is a schematic diagram of an alarm system 400 that is an embodiment of the invention . The alarm system 400 comprises a control panel 404 for controlling power supplied to a plurality of alarm units 402a-b of the alarm system. Each of the plurality of alarm units 402a-b may be substantially similar to the alarm unit 202 discussed above . A first power line 406 and a second power line 408 are connected to the control panel 404 , such that the control panel 404 can apply voltages to the first and second power lines 406 , 408 in order to convey power along the power lines . However , unlike control panels 204 and 304 , control panel 404 may not be configured to reverse polarities of the voltages applied to the first and second power lines 406 , 408 in order to perform continuous reverse polarity monitoring of the power lines when the alarm system is in the quiescent mode . Instead, the control panel 404 may be configured to monitor integrity of the first and second power lines 406 , 408 by transmitting a pulsed voltage along the first and second power lines 406 , 408 . The pulsed voltage may have a sufficiently short duration, and/or have a sufficiently small magnitude such that it does not cause any of the alarm units in the system to generate an alarm .

As shown in Fig . 4 , a switching module 410 is connected to the first and second power lines 406 , 408 , between the control panel 404 and the plurality of alarm units 402a-b . An input side of the switching module 410 is connected to first and second power lines 406 , 408 , whilst an output side of the switching module 410 is connected to a first output power line 412 and a second output power lines 414 . The plurality of alarm units 402a-b are connected in parallel to the first and second output power lines 412 , 414 , so that they can receive power therefrom. As indicated by the dashed lines in Fig . 4 , the first and second power output lines 412 , 414 may extend beyond the portion that is depicted in Fig . 4 . For instance further alarm units may be connected to the first and second power output lines 412 , 414 , and/or the first and second power output lines 412 , 414 may terminate with an EOL device ( similar to EOL device 114 ) connected between their distal ends .

The switching module 410 includes a first switch 416 and a second switch 418 which are configured to selectively couple the first output power line 412 to the first power line 406 or the second power line 408 , and to selectively couple the second output power line 414 to the second power line 408 or the first power line 406 . The first and second switches 416 , 418 are arranged such that , when the first switch 416 couples the first output power line 412 to the first power line 406 , the second switch 418 couples the second output power line 414 to the second power line 408 ( and vice versa ) . Thus , the first and second switches 416 , 418 may be controlled in order to swap voltages that are applied to the first and second power output lines 412 , 414 . The positions first and second switches 416 , 418 may be controlled manually, e . g . via a single toggle button, manual switch, or the like . In some cases , the switching module 410 may be operable with a key, e . g . a key may need to be inserted into a lock in the switching module 410 to enable the positions of first and second switches 416 , 418 to be changed . This may serve to avoid tampering with the switching module 410 .

To test the alarm units 402a-b, a user may first put the control panel 404 in alarm mode . In the alarm mode , the control panel 404 may apply a positive voltage to the first power line 406 and a negative voltage to the second power line 408 . The switching module 410 may then be operated such that the first switch 416 couples the first power line to the second output power line 414 , and the second switch 418 couples the second power line 408 to the first output power line 412 . In this configuration, there is thus a negative voltage on the first output power line 412 and a positive voltage on the second output power line 414 . Accordingly, due to the reversed polarity, the alarm units 402a-b do not generate an alarm ( for the reasons discussed above in relation to alarm unit 202 when in the quiescent mode ) . Then, the user may transmit a control signal to one of the alarm units 402a- b , to trigger the test mode in that alarm unit . The test mode for the alarm units 402a-b may function in the same was as discussed above for the alarm unit 202 .

Once the alarm units 402a-b have been tested, the user may switch the control panel back to the quiescent mode , and operate the switching module 410 so that the first switch 416 couples the first power line 406 to the first output power line 412 , and the second switch 418 couples the second power line 408 to the second output power line 414 . Then, if the alarm mode of the alarm system is triggered, voltages applied to the first and second power lines 406 , 408 are transmitted to the first and second output power lines 412 , 418 , respectively, such that the alarm units 402a-b generate an alarm . Accordingly, the switching module 410 may facilitate wireless testing of alarm units in an alarm system where the control panel is not itself configured to reverse the polarities of the voltages applied to the first and second power lines .

As shown in Fig . 4 , the switching module may optionally include first and second power input lines 420 , 422 , to which an auxiliary power supply can be connected for powering the alarm units 402a-b . The first and second switches 416 , 418 may then be arranged to selectively couple the first power input line 420 to the first output power line 412 or the second output power line 414 , and to selectively couple the second power input line 422 to the second output power line 414 or the first output power line 412 . Thus , the switching module 410 may also enable wireless testing of the alarm units 402a-b when an auxiliary power supply is used to power the alarm units 402a-b . Additionally as shown in Fig . 4 , the switching module 410 may comprise a set of diodes which are arranged to control a direction of current flow through the switching module 410 , e . g . from the input side towards the output side .