GB2604049A

GB2604049A - Alarm system

Info

Publication number: GB2604049A
Application number: GB2204445.7A
Authority: GB
Inventors: Andrew Veal James
Original assignee: Pyronix Ltd
Current assignee: Pyronix Ltd
Priority date: 2021-02-19
Filing date: 2021-02-19
Publication date: 2022-08-24
Anticipated expiration: 2041-02-19
Also published as: GB2604049B; GB202204445D0

Abstract

An alarm system includes a device that communicates wirelessly with a control portion. Supervision messages 200 are transmitted at supervision periods Ps from a device to a control portion to indicate device functionality and arm/disarm status (see Fig.4). In order to reduce battery usage at the device, the control portion may send reverse supervision messages 510 to the device to suppress transmission of supervision messages 200. Where a reverse supervision message is not received by the device within a supervision period Ps, the device transmits a supervision message as normal at the end of the supervision period Ps (see 5102 and 2002 of Fig.5b). The device may conserve power by turning off its transceiver until a scheduled time in order to receive reverse supervision message. The reverse supervision message 510 may indicate an intended arm state of the system or device and the device may change its armed state in response thereto. The device may be arranged to transmit supervision messages with at least a minimum frequency to allow tampering or a fault to be evident. A supervision fault period (PSF, Fig.10) and a poll fault period (PPF, Fig.11) may also be provided.

Description

ALARM SYSTEM

[0001] This application relates to alarm systems and elements for use in alarm systems. In particular, this application relates to alarm systems having devices or elements that communicate wirelessly.

BACKGROUND

[0002] Alarm systems may be wired, wireless or a combination thereof. Wireless alarm systems may be easier and less expensive to install than wired systems. However, wireless signaling may be less reliable than wired signaling, which may present challenges in maintaining performance of the alarm systems.

[0003] Wireless alarm systems may include battery powered elements (e.g. detectors or sensors that are not mains powered). Reducing power usage in these elements may extend battery life. Some approaches to increasing reliability of wireless communication (e.g. increasing transmission power or repeating transmissions) may increase power usage, and so be at odds with extending battery life of battery powered wireless elements.

BRIEF SUMMARY OF THE DISCLOSURE

[0004] In accordance with aspects of present invention there is provided a method, a device, a control portion, a computer program or a computer readable storage medium for use in an alarm system, as set out in the appended claims.

BRIEF DESCRIPTION OF THE DRAWINGS

[0005] Embodiments of the invention are further described hereinafter with reference to 25 the accompanying drawings, in which: Figure 1 illustrates an alarm system consistent with some examples.

Figure 2 illustrates an example of supervision messages between a device and a control portion.

Figure 3a illustrates an example of supervision messages between a device and a control portion Figure 3b shows another example of supervision messages between a device and a control portion.

Figure 4 shows an example of supervision messages and arm messages between a device and a control portion.

Figure 5a shows an example of supervision messages between a device and a control portion.

Figure 5b shows an example of messages between a device and a control portion in which a reverse supervision message is not received.

Figure 6 shows an example of messages between a device and a control portion.

Figure 7 shows an example of messages in a system using reverse supervision.

Figure 8 shows an example of signals in a system using reverse supervision.

Figure 9 shows an example of an arrangement in which no more than n consecutive supervisions may be suppressed.

Figure 10 shows an example of an arrangement in which a supervision fault period is defined.

Figure 11 shows an example of an arrangement in which a poll fault period is defined. Figure 12 shows a method that may be implemented in a device according to some examples.

Figure 13 shows a method according to some examples.

Figure 14 shows a method according to some examples.

Figure 15 shows a device suitable for use as a device of the alarm system.

Figure 16 shows an example of a device suitable for use as a hub or control portion of the system.

DETAILED DESCRIPTION

[0006] Figure 1 illustrates an alarm system 100 consistent with some examples. The alarm system 100 includes a control portion 110 and one or more devices 130. The control portion 110 may be a included in a single device. In some examples the functionality of the control portion 110 may be spread over two or more devices that cooperate to form the control portion 110. In such cases, the two or more devices may communicate over a wired or a wireless medium. In some examples, the control portion 110 may include a panel. The panel may include a key pad, display screen or other user interface elements. In some examples the alarm system 100 may include a panel that is not part of the control portion 110. The control portion 110 may be, or may include, a hub. It is to be understood that references to a hub herein may be substituted for a similar control portion 110. The control portion 110 may be arranged to wirelessly communicate with the devices 130.

[0007] Devices 130 may be elements of the alarm system, such as detection devices, bell boxes, sounders, key pads, touch screens, RFID readers, etc. The devices 130 may receive signals from the control portion 110 and may send signals to the control portion 110. For example, the control portion 110 may send control signals to the devices 130.

[0008] Where the device 130 is a sensor or detector, the control signals may set an armed/unarmed status of the device 130. The device 130 may signal a detection or activation to the control portion 110. Where the device 130 is a sounder or bell box the control portion 110 may send a signal to cause an alarm to be sounded. Where the device 130 is a key pad the device 130 may send a signal to the control portion 110 indicative of an input to the key pad.

Where the device 130 is an RFID reader the device 130 may send a signal to the control portion 110 indicative of information read from an RFID tag.

[0009] An element of the alarm system, such as the control portion, may be arranged to communicate with an external network 150, such as the Internet. This may be via a wired connection, a wireless connection or a combination of wired and wireless connections.

[0010] The device or devices forming the control portion may also perform other functions, such as sensing, sounding, key pad input, RFID reading, etc. [0011] The system may also include components that use wired communication. For example, where the system includes a hub and a panel, communication between the hub and panel could be wired instead of wireless. Similarly, the control portion may have a wired communication path to some devices 130.

[0012] In some examples, elements of the alarm system 100 may be connected to mains power. For example, the control portion 110, hub and/or panel may be mains powered in some examples. Some or all of the devices 130 may be battery powered. It is to be understood that mains powered elements may also be provided with a battery backup. Herein, unless otherwise stated, references to a mains powered element are intended to describe an element that is primarily mains powered but may be provided with an alternative power source, such as a backup battery. Similarly, references to a battery powered element are intended to describe an element that is primarily powered by a battery (or other energy storage device), typically without a connection to mains electricity. In some examples the devices 130 may be solely powered by a battery.

[0013] Devices 130 may transmit supervision messages to the control portion 110.

Supervision messages may be transmitted periodically. In some cases the periodicity of the supervision message may be approximate.

[0014] Supervision messages may be used in re-synchronizing clocks between a device 130 and the hub 110. This may allow the use of less accurate clocks in device 130, which may allow for reduced cost and/or power consumption. For example a low frequency (e.g. 32 KHz) crystal may be used in the clock of device 130, providing lower power consumption than a faster, more accurate crystal.

[0015] In some examples, supervision messages may provide information to the control portion 110 about the status (e.g. the state and/or performance) of the device 130, allowing the control portion 110 to confirm that the device 130 is operating correctly. In some examples, the control portion 110 may acknowledge receipt of the supervision message by sending an Ack message to the device 130 that sent the supervision message. In some examples, a device 130 may retransmit supervision messages until an Ack is received from the control portion 110.

[0016] Supervision messages use power of the transmitting device 130, so increasing the period between supervision messages allows for a reduction in power consumption, leading to an increase in battery life for battery powered devices 130. For every regular supervision message transmission by battery powered device 130, a portion of the device's battery capacity will be consumed. Regular supervision messages can consume a large percentage of overall battery capacity over the lifetime of the battery. Further, reducing the number of supervision messages reduces RF bandwidth usage. However, increasing the period between supervision messages (e.g. by reducing the number of supervision messages) may reduce reliability of the alarm system 100.

[0017] In some examples a supervision fault period may be defined. If a device 130 has not communicated with the control portion 110 for a period of time exceeding the supervision fault period, this may be signaled as a fault. For example, this may be considered indicative of a problem such as a failure of the device 130, or a failure of the communication path from the device 130 to the control portion 110. The time period between supervision messages from the device 130 may be set to be less than the supervision fault period, such that the receipt of the supervision messages by the control portion 110 will prevent expiry of the supervision fault period when the system 100 is operating correctly. In some examples a timer at the control portion 110 for monitoring the supervision fault period associated with a device 130 may be reset each time a supervision message is received from the device 130.

[0018] Figure 2 illustrates an example of supervision messages 200 between a device 130 and a control portion 110. The first supervision message 2001 is sent from the device 130 and received successfully by the control portion 110. In response, the control portion 110 starts a timer for supervision fault period 2101, having duration PsF. The timer may be implemented in various ways. For example, a register may store a time stamp of receipt of the supervision message 2001. Subsequently, the time stamp may be compared with a current time from a clock of the control portion 110 to determine the time elapsed since receipt of the supervision message 200. Alternatively, a time of the expiry of the supervision fault period 2101 may be determined based on the time of receipt of the first supervision message 2001, and the expiry time stored in a register. The value in the register may then be compared with the clock of the control portion 110 to determine if the period 2101 has expired.

[0019] When a period Ps, corresponding to the supervision period, has elapsed since the first supervision message 2001, a second supervision message 2002 is transmitted by the device 130 and received by the control portion 110. The second supervision message 2002 is received before expiry of the supervision fault period 2101. The receipt of the second supervision message 2002 by the control portion 110 causes the control portion 110 to reset the clock (e.g. by updating the fimestamp in the register). The third supervision message 2003 is transmitted after a period of time R following the transmission of the second supervision message 2002, and is received by the control portion 110. The supervision fault period 2102 has not expired when the third supervision message 2003 is received. The timer is reset by the control portion 110 and measurement of supervision fault period 2103 is started. The subsequent supervision messages 2004, 2005 are not received by the control portion 110. This may be due to a fault at the device 130 or due to a source of interference, for example. The supervision fault period 2103 expires without a supervision message being received, and so the control portion 110 may issue a warning indicative of the loss of communication from the device 130.

[0020] The supervision period Ps may be shorter than the supervision fault period PsF. In the example of Figure 2 the supervision fault period PsF is more than twice the duration of the supervision period Ps. However, the supervision fault period PsF may include more or fewer supervision periods P. [0021] In some examples a poll fault period may be defined. If a device 130 has not communicated with the control portion 110 in a poll fault period preceding an arm condition at the control portion 110 (or at a panel external to the control portion 110), this may be signaled as a potential fault. The time period between supervision messages from the device 130 may be set to be less than the poll fault period. Accordingly, if the supervision messages are successfully received by the control portion 110, when an arm condition is set the period between receipt of the last received supervision message and the setting of the arm condition will be less than the poll fault period.

[0022] Figure 3a illustrates an example of supervision messages 200 between a device 130 and a control portion 110. The first, second and third supervision message 2001, 2002, 2003 are sent from the device 130 and received successfully by the control portion 110. After the third supervision message 2003 is sent to the control portion 110 the control portion 110 may receive an arm instruction 230 instructing the control portion 110 to arm the alarm system 100. The arm instruction 230 may be received from a panel or a user input device in the system 100, for example. The control portion 110 then determines whether a supervision message 200 has been received in the period 240 of duration PpF immediately preceding the receipt of the arm instruction 230, where the period PpF is the poll fault period. In some examples a timestamp of the most recently received supervision message 200 (in this example the third supervision message 2003) may be stored in a register by the control portion 110 or by a device that is not part of the control portion 110, such as a panel external to the control portion 110. A difference between the stored timestamp and a time of receipt of the arm instruction may be compared with the poll fault period PpF. In the example of Figure 3a, the third supervision message 2003 was received in the period 240, and so no warning is triggered.

[0023] Figure 3b shows another example of supervision messages 200 between a device 130 and a control portion 110. The first, second and third supervision message 2001, 2002, 2003 are sent from the device 130. However, only the first supervision message 2001 is received successfully by the control portion 110. Supervision messages 2002, 2003 are not received (e.g. due to a failure of device 130 or signal interference). The control portion 110 receives an arm instruction 230 instructing the control portion 11010 arm the alarm system 100. In this example the arm instruction 230 is received after the third supervision message 2003 was scheduled to be sent/received. The control portion 110 then determines that no supervision message 200 has been received in the poll fault period 240 of duration PpF immediately preceding the receipt of the arm instruction 230. In some examples a timestamp of the most recently received supervision message 200 (in this example the first supervision message 2001) may be stored in a register by the control portion 110 and a difference between the stored timestamp and a current time may be compared with the poll fault period PpF. In the example of Figure 3b, no supervision message 2003 was received in the period 240, and so a warning is triggered.

[0024] The supervision period P, may be shorter than the poll fault period PpF. In the example of Figures 3a and 3b the poll fault period PpF is more than the duration of the supervision period P. In some examples, the poll fault period PpF may include multiple supervision periods Ps (PpF nPs, n 2).

[0025] When an arm condition is set (e.g. at panel 120) for a device 130, this may be communicated to the device 130 by the control portion 110. If the communication of the arm status is not received by the device 130 the device will not become armed until the next supervision transaction for that device 130, when the unarmed state of the device will be reported to the control portion 110 in a supervision message, at which time the control portion 110 can send another instruction to the device 130 to arm. This instruction to arm may be sent immediately on a per-device basis, or may be a broadcast message to arm all devices.

Accordingly a longer supervision period (i.e. period between transmission of supervision messages) may lead to an increase in the time between an armed state being set and the device 130 being armed. In this time period, an occurrence that should lead loan alarm condition being set by device 130 (e.g. the presence of an intruder in a detection zone of device 130) would not be detected by the unarmed device 130.

[0026] Figure 4 shows an example of supervision messages 200 and arm messages 250, 260 between a device 130 and a control portion 110. First and second supervision message 2001, 2002 are sent from the device 130 and received by the control portion 110. The control portion 110 then receives an arm instruction 230 and transmits an arming signal 250 (e.g. broadcast signal) indicating that the device 130 (and possibly other devices) are to enter an armed state. However, in this example the arming signal 250 is not received by the device 130.

Subsequently, the next supervision message 2003 is transmitted by the device 130 and received by the control portion 110. As supervision messages 200 from device 130 indicate a status the device 130 (e.g. armed or unarmed) the control portion 110 may determine, on receipt of the supervision message 2003, that device 130 is not armed and may send a further arming signal 260 to the device 130 to cause the device 130 to arm. As can be seen from Figure 4, an upper limit on the delay between arming signal 250 and arming signal 260 is the supervision period Ps (assuming the period between receiving supervision message 2003 and sending the arming signal 260 is negligible).

[0027] EN 50131 is a European standard defining four grades of alarm system. In an EN graded wireless security system all EN graded devices are to perform regular supervision transmissions to a control portion (e.g. a panel). These messages allow the control portion to understand if the devices are still working and are able to, for example, contribute to the detection of intruders in the current arm period. The standard includes a requirement that if a device has not communicated to a controller of the system in the last 2 hours, this must be signaled. This corresponds with the supervision fault period, described above being 2 hours. In addition, the standard indicates that if a device has not communicated in the 20 minutes preceding an arm condition at the panel 120, this must be flagged to the user at the time of arming. This corresponds to the poll fault period, described above, being 20 minutes. As a result of these requirements, an EN graded system may have a supervision period that is less than 20 minutes. As explained above, the supervision period may be linked to an upper limit for a delay between arming a system at the panel 120 and a device 130 being armed. In some examples an arming delay of the order of 20 minutes is undesirable, and so in some systems the supervision period may be shorter than 20 minutes to avoid excessive arming delays.

[0028] In some examples, devices 130 within the alarm system 100 may have different supervision periods. For example, the supervision period may be set as a multiple of a 300 s (5 minute) period. So, for example, supervision periods may be selected from 5, 10 and 15 minutes. This allows control over the supervision period, so where it is determined that it is acceptable for a first device 130 to have a longer supervision period than a second device 130, the first device 130 may be assigned a longer supervision period than the second device 130, leading to reduced power consumption and increased battery life of the first device 130.

[0029] In some examples the control portion 110 may control the supervision period on a per-device basis. In some examples a supervision period for a device 130 may be changed at any time by the control portion 110. In such cases, the next supervision response (e.g. an acknowledgement, Ack, of receipt of the supervision message) from the control portion 110 to that device 130 may update the device supervision period.

[0030] Figure 5a shows an example of supervision messages 200 between a device 130 and a control portion 110 according to some examples. In this example the control portion 110 may send a reverse supervision message 510 to the device 130 to suppress transmission of the next supervision message 200. In the example of Figure 5a, a first supervision message 2001 is sent from the device 130 to the control portion 110. During the supervision period 5201 that begins with the transmission of supervision message 2001, the control portion 110 sends a reverse supervision message 5101 to the device 130. The device 310 determines that the reverse supervision message 5101 has been received (in period 5201) and in response suppresses (i.e. omits or does not send) the next (second) supervision message, which is scheduled to occur at 5001. Similarly, during the next supervision period 5202, which begins at the time scheduled for the suppressed second supervision message 5001, the device 130 receives a second reverse supervision message 5102 from the control portion 110. In response to receiving the second reverse supervision message 5102 (in the period 5202) the device 130 suppresses the next supervision message at 5002 that is associated with the period 5202 (as period 5202 immediately precedes/ends with 5002).

[0031] In some examples, where a reverse supervision message is not received by the device 130 within a particular supervision period Ps (e.g. because of interference or because the control portion 110 has not transmitted a reverse supervision message) the device 130 transmits a supervision message 200 as normal at the end of that supervision period Ps. Figure 5b shows an example in which reverse supervision message 5102 is not received at device 130 in supervision period 5202. Accordingly, at the end of the supervision period in which reverse supervision message 5102 was (or would have been) transmitted, device 130 transmits a supervision message 2002.

[0032] The reverse supervision message 510 may be a broadcast message to all devices 130 in the system 100. Where devices 130 in the system 100 conserve power by turning off their transceiver, or placing the transceiver in a sleep state, the devices may be aware of the scheduled timing of the reverse supervision message 510 and may power up the transceiver around the scheduled time in order to receive the reverse supervision message 510.

[0033] The reverse supervision message 510 may indicate the intended arm state of the system or device 130. Where the current armed state of the device 130 disagrees with the armed state indicated in the reverse supervision message 510 the device 130 may change its armed state, in response to receiving the reverse supervision message 510, so that the armed state of the device 130 matches the armed state indicated in the reverse supervision message 510.

[0034] By using reverse supervision messages 510, an excessive delay between an arm instruction 230 being received at the control portion 110 and device 130 entering an armed state can be limited to less than a period between supervision messages. This may allow a reduction in a transmission frequency of supervision messages 200 without a corresponding increase in the period for arming the device 130. Figure 6 shows an example in which supervision messages at 5001, 5002 and 5003 are suppressed due to receipt at device 130 of reverse supervision messages 5101, 5102, 5103. Following reverse supervision message 5101 the control portion 110 receives an instruction 230 to arm the alarm system 100 and transmits an arming signal 250 that is not received by the device 130 (e.g. due to interference). No supervision message 200 is transmitted at 5001, and so the incorrect arm state of the device 130 is not detected at that point. The reverse supervision message 5102 is then transmitted by the control portion 110 and received by device 130. The reverse supervision message 5102 indicates that the device 130 should be in an armed state. On receipt of the reverse supervision message 5102 the device determines that it should transition to an armed state and changes its state to the armed state accordingly. As can be seen, a period between reverse supervision messages PRs may define an upper limit between the receipt of an arm instruction 230 and receipt at the device 130 of an instruction to enter the armed state (assuming that the reverse supervision message 5102 is received by the device 130). Further, this upper limit does not depend on the transmission of supervision messages 200 by the device 130. Accordingly, the number of transmissions by the device 130 may be reduced On particular, by reducing the number of supervision messages 200 transmitted by the device 130) without a corresponding increase in an upper limit on a delay in arming the device 130 following an arm instruction 230. The repeat period of the reverse supervision messages PRs may be the same as or less than the supervision period P5. In some examples, the reverse supervision period PRs may be greater than the supervision period P5.

[0035] If all supervision messages from a device 130 are suppressed and the device becomes inoperable (e.g. through tampering or a fault), this will not be evident at the control portion 110.

Accordingly, the device 130 may be arranged to transmit supervision messages 200 with at least a minimum frequency. For example, if a time since the last supervision message was transmitted exceeds a threshold value, the next scheduled supervision message may be transmitted, even if a reverse supervision message is received in the immediately preceding supervision period. Devices that have ceased communication may be detected by implementing a supervision fault period, as described in relation to Figure 2.

[0036] Figure 7 shows an example of signals in a system using reverse supervision, as described in relation to Figures 5 and 6, and also applying a supervision fault period, as described in relation to Figure 2. In the example of Figure 7, reverse supervision messages 5101, 5102, 5103 are received by device 130, and so supervision messages 200 are not transmitted (are suppressed) at 5001, 5002, 5003. In this example, the supervision fault period PsF 2101 would begin with the receipt of supervision message 2001 and, as subsequent supervision messages 200 are suppressed, the supervision fault period Psp 2101 would expire before a next supervision message 200 is received. Accordingly, this arrangement may lead to unnecessary warnings being issued.

[0037] Figure 8 shows an example of signals in a system using reverse supervision, as described in relation to Figures 5 and 6, and also applying a poll fault period, as described in relation to Figures 3a and 3b. In the example of Figure 8, reverse supervision messages 5101, 5102, 5103 are received by device, and so supervision messages 200 are not transmitted (are suppressed) at 5001, 5002, 5003. In this example, an arm instruction 230 is received following reverse supervision message 5103. As supervision messages 200 were suppressed at 5001, 5002, 5003 no supervision messages were received in the poll fault period PpF immediately preceding receipt of the arm instruction 230 by the control portion 110. As a result a warning may be issued. As there is not necessarily a fault or problem with communication between the control portion 110 and device 130 a warning in these circumstances may be inappropriate.

[0038] In some examples a supervision message 200 may not be suppressed in response to receipt of a reverse supervision message 510 if the time since the last supervision message was transmitted would exceed a threshold value. In some examples the threshold value may be an integer multiple of the supervision period. In some examples the integer multiple may be three. In some examples no more than a predetermined number of consecutive supervision messages 200 may be suppressed. In some examples, the predetermined number may be two.

[0039] Figure 9 shows an example of an arrangement in which no more than n consecutive supervisions may be suppressed, where n is 2. In some examples n may take other values and may be an integer or non-integer number. In this example, supervision message 2001 is transmitted, but supervision messages at 5001 and 5002 are suppressed due to the receipt at the device 130 of reverse supervision messages 5101 and 5102. In the supervision period following the suppressed supervision message at 5102 a reverse supervision message 5103 is received at device 130. Device 130 determines that two consecutive supervision messages at 5001 and 5002 immediately preceding the supervision period 5203 starting at 5002 have been suppressed, and so the next supervision message 2002 at the end of supervision period 5203 is not suppressed, notwithstanding the receipt of a reverse supervision message 5103 in that supervision period.

[0040] Figure 10 shows an example of an arrangement according to the example in Figure 9 in which a supervision fault period PsF is defined. In this example the supervision fault period PsF and/or the supervision period Ps is set such that the supervision fault period PsF is greater than three supervision periods P. Thus, a supervision message 2002 is transmitted to the control portion 110 before the end of the supervision fault period. In this way, inappropriate warning messages may be avoided while reducing the number of supervision messages to be transmitted by device 130.

[0041] Figure 11 shows an example of an arrangement according to the example in Figure 9 in which a poll fault period PpF is defined. In this example the poll fault period PpF and/or the supervision period Ps is set such that the poll fault period PpF is greater than three supervision periods P. In this example, an arm instruction 230 may be received in the supervision period R that starts at 5002. The two preceding supervision messages at 5001 and 5002 have been suppressed, but the supervision message 2001 immediately preceding these was transmitted (and, in this example, was received by the control portion 110). Accordingly, supervision message 2001 was received by the control portion 110 within the period PpF immediately preceding the receipt of the arm instruction 230 and no warning is issued. Accordingly, inappropriate warning messages may be avoided while retaining the benefit of reducing the number of supervision messages to be transmitted by device 130. If the arm instruction had been received more than PpF after the receipt of the first supervision message 2001, the arm instruction would have been received after scheduled transmission time of supervision message 2002, as PpF > 3 Ps and in this example it is assumed that no more than two consecutive supervision messages 200 may be suppressed. Hence, supervision message 2002 is successfully received by control portion 110, no warning would be issued.

[0042] In some examples a maximum time period between supervision messages 200 may be set, such that a supervision message 200 will not be suppressed if the time between transmission of the last (non-suppressed) supervision message 200 and the next scheduled supervision message 200 would be greater than the maximum time period. Alternatively, a threshold may be set, such that a supervision message 200 will not be suppressed if, at the time the supervision message 200 is scheduled, the time since the last transmitted (non-suppressed) supervision message 200 is greater than the threshold. In some examples, the maximum time period or threshold may be a multiple of a supervision period.

[0043] Where a supervision fault period has been set in the system 100, a maximum time period between supervision messages 200 (or a threshold, etc.) may be such that at least one supervision transmission is to be transmitted in each supervision fault period. That is, the maximum time period between non-suppressed supervision messages is less than the supervision fault period.

[0044] Where a poll fault period has been set in the system 100, a maximum time period between supervision messages 200 (or a threshold, etc.) may be such that at least one supervision transmission is to be transmitted in each poll fault period. That is, the maximum time period between non-suppressed supervision messages is less than the poll fault period.

[0045] In some examples, a reverse supervision period may be determined based on an upper limit on an acceptable delay in arming the system.

[0046] In some examples, the supervision period may be selected to be 5 minutes, and the maximum period between non-suppressed supervision transmissions may be selected to be 15 minutes. The reverse supervision period may be equal to the supervision period (e.g. 5 minutes). A supervision fault period may be set at 2 hours. A poll fault period may be set at 20 minutes. In such examples, the supervision fault period and poll fault period would comply with the requirements of EN 50131 and the delay between an alarm instruction from a user and a device 130 receiving an arming signal would be expected to be less than 5 minutes. Other time periods may be set to meet performance requirements of the system. Different devices 130 within the system 100 may have different time periods (e.g. supervision periods) from each other. In some examples a supervision period of a device 130 may be changed in response to an instruction from the control portion 110.

[0047] In some examples the device 130 may reduce power to a transceiver (e.g. putting it in a sleep mode or powering it down) when the transceiver is not in use. In such cases, the device 130 may receive information (e.g. in a message from the control portion 110 prior to powering down the transceiver) regarding the timing of scheduled reverse supervision messages and the device 130 may wake up or power up the transceiver at the time scheduled for the reverse supervision message in order to receive the reverse supervision message.

[0048] In some examples the device 130 may be a detector or sensor of the alarm system. The detector may be arranged to detect an event and send an alarm signal in response to that event. The alarm signal may be sent separately from supervision messages 200 transmitted by the device 130. This may allow an alarm message to be transmitted more quickly, rather than waiting for the next scheduled supervision message 200. Examples of detectors and sensors include passive infrared sensors, microwave sensors, door or window sensors, etc. [0049] Figure 12 shows a method 1200 that may be implemented in a device 130 according to some examples. At 1210 it is determined whether a supervision period has expired. When a supervision period has expired the method proceeds to 1220, where it is determined whether a reverse supervision message was received in that supervision period. If no reverse supervision message was received in that supervision period then a supervision message is sent at 1230. However, if a reverse supervision message was received in that supervision period it is determined, at 1240 if the maximum number of consecutive supervision messages have been suppressed, or if a threshold time since a last supervision transmission has been exceed. If so, a supervision message is sent at 1230, otherwise no supervision message is sent, as denoted at 1250. A new supervision period begins at 1260 and the method returns to 1210.

[0050] Figure 13 shows a method 1300 according to some examples. At 1310 a device 130 in an alarm system receives a reverse supervision message in a first period, where the first period is a period between consecutive planned or scheduled supervision messages that are to be transmitted by the device 130. At 1320, in response to receiving the reverse supervision message, the device 130 suppresses (i.e. does not send) a supervision message associated with the first period. For example the associated supervision message may be a supervision message that was planned or scheduled to be transmitted at the end of the first period.

[0051] Figure 14 shows a method 1400 according to some examples. At 1410 a control portion 110 transmits (or causes transmission of) a reverse supervision message for reception by one or more devices 130 in the alarm system, the reverse supervision message may including armed status information. Reverse supervision messages may be transmitted periodically by the control portion 110. The reverse supervision message may cause a device 130 that receives it to suppress a subsequent supervision message.

[0052] Figure 15 shows a device 1500 suitable for use as a device 130 of the alarm system 100. The device 1500 may include processing circuitry 1510. The processing circuitry 1510 may include a processor 1520 and memory 1530, for example. The device 1500 may also include wireless communication circuitry 1540 for receiving signals, such as reverse supervision messages, and for transmitting signals, such as supervision messages. The device 1500 may also include alarm system components 1550 to provide functionality in the alarm system 100, such as one or more of a sensor, a sounder, a light, a key pad, an RFID reader, etc. The components of the device 1500 may communicate through a communication medium, such as a bus 1560.

[0053] Figure 16 shows an example of a device 1600 suitable for use as a control portion 110 (e.g. a hub) of the system 100. The device 1600 may include processing circuitry 1610. The processing circuitry 1610 may include a processor 1620 and memory 1630, for example. The device 1600 may also include wireless communication circuitry 1640 for receiving signals, such as supervision messages, and for transmitting signals, such as reverse supervision messages. The components of the device 1600 may communicate through a communication medium, such as a bus 1660.

[0054] In some examples the devices described herein, such as devices 120, 110, 130, 140, 1500 or 1600, may be controlled by a computer program. Similarly, the methods described herein, such as methods 1200, 1300, 1400 may be implemented by a computer program. A computer program may be embodied in software, firmware, etc. The computer program may be stored as computer readable instructions on a computer readable storage medium, such as a memory device 1530, 1630, optical storage device, etc.. The medium may be a non-transitory storage medium.

[0055] Throughout the description and claims of this specification, the words "comprise" and "contain" and variations of them mean "including but not limited to", and they are not intended to (and do not) exclude other components, integers or steps. Throughout the description and claims of this specification, the singular encompasses the plural unless the context otherwise requires. In particular, where the indefinite article is used, the specification is to be understood as contemplating plurality as well as singularity, unless the context requires otherwise.

[0056] Features, integers, characteristics, or groups described in conjunction with a particular aspect, embodiment or example of the invention are to be understood to be applicable to any other aspect, embodiment or example described herein unless incompatible therewith. All of the features disclosed in this specification (including any accompanying claims, abstract and drawings), and/or all of the steps of any method or process so disclosed, may be combined in any combination, except combinations where at least some of such features and/or steps are mutually exclusive. The invention is not restricted to the details of any foregoing embodiments.

The invention extends to any novel one, or any novel combination, of the features disclosed in this specification (including any accompanying claims, abstract and drawings), or to any novel one, or any novel combination, of the steps of any method or process so disclosed.

100571 The reader's attention is directed to all papers and documents which are filed concurrently with or previous to this specification in connection with this application and which are open to public inspection with this specification, and the contents of all such papers and documents are incorporated herein by reference.

The following section of the description relates to further examples. The numbered paragraphs in this section are not claims. The claims are set forth below in the later section headed "claims".

1. A method for use in a device, the device to be used in an alarm system, the method comprising: receiving, in a first period, a reverse supervision message from a control portion of the alarm system, wherein the first period is a predetermined period between consecutive planned supervision messages, and suppressing a supervision message associated with the first period in response to receiving the reverse supervision message.

2. The method of clause 1, wherein the reverse supervision message indicates armed status information.

3. The method of any preceding clause, wherein no more than a predetermined number, n, of consecutive supervision messages are suppressed.

4. The method of clause 1 or clause 2, wherein in a second period corresponding to another predetermined period between consecutive planned supervision messages, in response to a determination that the previous n consecutive supervision messages have been suppressed, transmitting the supervision message associated with the second period regardless of whether or not a reverse supervision message is received in the second period.

5. The method of clause 3 or clause 4, wherein n is 2.

6. The method of any one of clauses 3 to 5 wherein the first period multiplied by n has a duration of less than 20 minutes, or wherein the first period multiplied by n has a duration of 15 minutes.

7. A device for use in an alarm system, the device comprising: wireless communication circuitry, and processing circuitry, wherein the processing circuitry is arranged to: determine whether or not a reverse supervision message has been received, via the wireless communication circuitry, in a first period, wherein the first period is a predetermined period between consecutive planned supervision messages, and in response to determining that the reverse supervision message has not been received, transmitting, via the wireless communication circuitry, a supervision message, and in response to determining that the reverse supervision message has been received, omitting transmission of the supervision message.

8. The device of clause 7, wherein the reverse supervision message indicates armed status information.

9. The device of clause 7 or clause 8, wherein the processing circuitry is further arranged to: determine that supervision messages have not been transmitted in a previous n consecutive periods for transmission of supervision messages, in response to receipt, via the wireless communication circuitry, of respective reverse supervision messages, and in response to the determination that the supervision messages have not been transmitted, transmitting a next supervision message regardless of receipt of a corresponding reverse supervision message.

10. The device of clause 7, wherein n is 2.

11. A method for use in a control portion of an alarm system, the method comprising: transmitting periodic reverse supervision messages for reception by one or more devices in the alarm system, the reverse supervision message including armed status information.

12. The method of clause 11 wherein the reverse supervision message includes an indication of an arm status of the one or more devices.

13. The method of clause 11 or clause 12 wherein the reverse supervision message is to cause a device that receives it to supress a corresponding supervision message.

14. The method of any one of clauses 11 to 13, wherein a period of the periodic reverse supervision messages is equal to a supervision period for the device.

15. The method of any one of clauses 11 to 13, wherein a period of the periodic reverse supervision messages is less than at least one of a supervision fault period and a poll fault period defined for the alarm system.

16. The method of clause 15, wherein the control portion s to trigger a warning if no supervision message has been received from a device of the one or more devices for a period of time exceeding the at least one of the supervision fault period and the poll fault period.

17. A control portion for use in an alarm system, the device comprising: wireless communication circuitry, and processing circuitry, wherein the processing circuitry is arranged to: cause transmission of periodic reverse supervision messages for reception by one or more devices in the alarm system, the reverse supervision message including armed status 30 information.

18. The control portion of clause 17 wherein the reverse supervision message includes an indication of an arm status of the one or more devices.

19. The control portion of clause 17 or clause 18 wherein the reverse supervision message is to cause a device that receives it to supress a corresponding supervision message.

20. The control portion of any one of clauses 17 to 19, wherein a period of the periodic reverse supervision messages is equal to the supervision period for the device.

21. The control portion of any one of clauses 17 to 19, wherein a period of the periodic reverse supervision messages is less than at least one of a supervision fault period and a poll fault period defined for the alarm system.

22. The control portion of clause 21, wherein the control portion is to trigger a warning if no supervision message has been received from a device of the one or more devices for a period of time exceeding the at least one of the supervision fault period and the poll fault period.

23. A computer program comprising instructions to cause a processing means to carry out the method of any one of clauses 1 to 6 or 11 to 16.

24. A computer readable storage medium storing instructions that, when performed by a processing means, causes the processing means to carry out the method of any one of clauses 1 to 6 or 11 to 16.

Claims

CLAIMS1. A method for use in a control portion of an alarm system, the method comprising: transmitting periodic reverse supervision messages for reception by one or more devices in the alarm system, the reverse supervision message including armed status information.
2. The method of claim 1 wherein the reverse supervision message includes an indication of an arm status of the one or more devices.
3. The method of claim 1 or claim 2 wherein the reverse supervision message is to cause a device that receives it to supress a corresponding supervision message.
4. The method of any one of claims 1 to 3, wherein a period of the periodic reverse supervision messages is equal to a supervision period for the device.
5. The method of any one of claims 1 to 3, wherein a period of the periodic reverse supervision messages is less than at least one of a supervision fault period and a poll fault period defined for the alarm system.
6. The method of claim 5, wherein the control portion s to trigger a warning if no supervision message has been received from a device of the one or more devices for a period of time exceeding the at least one of the supervision fault period and the poll fault period.
7 A control portion for use in an alarm system, the device comprising: wireless communication circuitry, and processing circuitry, wherein the processing circuitry is arranged to: cause transmission of periodic reverse supervision messages for reception by one or more devices in the alarm system, the reverse supervision message including armed status information.
8. The control portion of claim 7 wherein the reverse supervision message includes an indication of an arm status of the one or more devices.
9. The control portion of claim 7 or claim 8 wherein the reverse supervision message is to cause a device that receives it to supress a corresponding supervision message.
10. The control portion of any one of claims 7 to 9, wherein a period of the periodic reverse supervision messages is equal to the supervision period for the device.
11. The control portion of any one of claims 7 to 9, wherein a period of the periodic reverse supervision messages is less than at least one of a supervision fault period and a poll fault period defined for the alarm system.
12. The control portion of claim 11, wherein the control portion is to trigger a warning if no supervision message has been received from a device of the one or more devices for a period of time exceeding the at least one of the supervision fault period and the poll fault period.
13. A computer program comprising instructions to cause a processing means to carry out the method of any one of claims 1 to 6
14. A computer readable storage medium storing instructions that, when performed by a processing means, causes the processing means to carry out the method of any one of claims 1 to 6.