GB2377305A

GB2377305A - Radio frequency alarm system

Info

Publication number: GB2377305A
Application number: GB0109455A
Authority: GB
Inventors: Michael Garbutt; Paul Scorer
Original assignee: HARRISON BROTHERS STEEPLEJACKS
Current assignee: HARRISON BROTHERS STEEPLEJACKS
Priority date: 2001-04-18
Filing date: 2001-04-18
Publication date: 2003-01-08
Also published as: WO2002084620A1; GB0109455D0

Abstract

A radio frequency wireless alarm system, e.g. fire alarm system 1, comprises a plurality of control panels 2 in communication with a series of fire detectors 3, arranged in a series of zones 4. Each detector 3 transmits radio frequency signals to its associated control panel 2. Each of the control panels 2 communicates with its associated detectors 3 independently of the other control panels, by means of successive timing cycles (Fig. 2) such that simultaneous transmission of signals by more than one detector 3 to a single control panel 2 is prevented. A synchronisation signal is broadcast by one or more of the control panels (e.g. central control panel CP0) to all the other control panels and detectors in the system to synchronise their operation. An alarm signal can be transmitted from one of the control panels CP1 to CP4 to central control panel CP0, which then transmits the alarm signal to the other control panels.

Description

23,730S

RADIO FREQUENCY ALARM COMMUNICATION SYSTEM

The present invention relates to radio frequency alarm communication systems, and relates particularly, but not exclusively, to radio frequency wireless fire alarm systems.

A wireless radio frequency detection system is described in GB2288263. In that system, a plurality of monitoring units in the form of control panels are in radio communication with associated detectors and alarm sounders. Transmission of signals between the control panels and detectors occurs according to predetermined time slots controlled by the control units, and synchronization of the operation of the system is controlled by regular transmission by the control panels of a common time reference signal According to an aspect of the present invention, there is provided a radio frequency alarm communication system comprising: a plurality of control units, wherein a plurality of first said control units are adapted to communicate by radio with a second said control unit; at least one respective signal input device associated with each said control unit, for generating an alarm signal in an alarm situation; and a respective radio transmitter for transmitting the or each said alarm signal from the or each said signal input device by radio to the associated control unit; wherein said control units are adapted to operate independently of each other and the timing of transmission of said

-2 transmitters associated with a said control unit is arranged such that simultaneous transmission of signals by more than one transmitter to a single control unit is prevented, and said second control unit is adapted to receive an alarm signal from a said first control unit and transmit said alarm signal directly to the or each other said first control unit.

By providing control units which are adapted to operate independently of each other, this provides the advantage that even if one of the control units becomes inoperable, for example by being damaged by fire in the case that the system is a fire alarm system, the remainder of the system remains operable because the other control units continue to operate.

Also, by providing an arrangement in which the second control unit is adapted to receive an alarm signal from a first control unit and transmit the alarm signal directly to the or each other first control unit, this provides the advantage that the alarm signal can be communicated more rapidly to the other control units than in the case of the prior art, in which the

alarm signal is sequentially transmitted between control units.

This also provides the advantage of minimising cumulative timing errors which would arise in the case of an alarm signal being sequentially transmitted between control units.

At least one said control unit may be adapted to transmit data to at least one other said control unit.

Said data may include a timing signal to synchronism operation of a plurality of said control units.

This provides the advantage of enabling simultaneous transmission by transmitters associated with adjacent control units to be avoided, to minimise risk of signal clashing between transmitters in adjacent sectors of the system.

-3 Said data may include an indication of the status of said control unit.

This provides the advantage of enabling an alarm condition or failure of the control unit to be communicated to other control units in the system.

A plurality of said transmitters may be adapted to transmit data relating to the associated signal input device to the corresponding control unit.

Said data may include data relating to the status of said signal input device.

This provides the advantage of enabling failure or low battery power of a signal input device to be communicated to the associated control unit to enable remedial action to be taken.

At least one said control unit may be adapted to transmit a timing signal to the or each said transmitter associated therewith to synchronism operation of the timing of said transmitters. This provides the advantage of enabling signal clashing between transmitters to be avoided without necessitating the use of expensive timer devices which remain accurate for long periods.

Said second control unit is preferably the control unit capable of radio communication with the largest number of said first control units.

This provides the advantage of enabling alarm signals to be communicated as rapidly as possible to the largest number of control units.

-4 In a preferred embodiment, in the event of failure of said second control unit, the system is adapted to transmit a said alarm signal to said first control units by sequentially transmitting said signal between said first control units.

At least one said signal input device may be a fire and/or smoke detector.

At least one said signal input device is preferably an alarm communication device.

The system may further comprise at least one alarm sounder for producing an audible alarm signal, said sounder being associated with a said control unit and adapted to be actuated by means of an actuation signal from the associated control unit. At least one said alarm sounder may be adapted to receive electrical power intermittently according to a signal from the associated control unit.

This provides the advantage of enabling battery power of the alarm sounder to be preserved.

The system in use may carry out successive timing cycles in which each said transmitter sends a signal to the associated control unit.

According to another aspect of the present invention, there is provided a radio frequency alarm communication method comprising: generating an alarm signal in an alarm situation;

-s - transmitting said alarm signal by radio directly to an associated control unit, wherein a plurality of first said control units are adapted to communicate by radio with a second said control unit, said control units are adapted to operate independently of each other and the timing of transmission of said alarm signal is arranged such that simultaneous transmission of more than one said alarm signal to a single said first control unit is prevented; if the associated said control unit is a said first control unit, transmitting said alarm signal directly by radio to said second control unit; and transmitting said alarm signal from said second control unit directly to the or each other said first control unit.

The method may further comprise the step of transmitting data from at least one said control unit to at least one other said control unit.

Said data may include an indication of the status of said control unit.

The method may further comprise the step of selecting said second control unit such that said second control unit is the control unit capable of radio communication with the largest number of said first control units.

The method may further comprise the step of transmitting a said alarm signal to said first control units by sequentially transmitting said signal between said first control units in the event of failure of said second control unit.

-G A preferred embodiment of the invention will now be described, by way of example only and not in any limitative sense, with reference to the accompanying drawings, in which: Figure 1 is a schematic representation of a fire detection system embodying the present invention; Figure 2 indicates the content of a timing cycle used in the operation of the system of Figure 1; Figures 3A to 3J show more detailed information of the timing cycle of Figure 2; Figure 4 is an illustration of the process of normal synchronization of the system of Figure 1; and Figure 5 is an illustration of the synchronization of the system of Figure 1 when a control panel fails.

Referring to Figure 1, a radio frequency wireless fire alarm system 1 has a series of control panels 2, shown in the figure as CPO to CP4' although it will be appreciated by persons skilled in the art that any number of control panels may be used. Each of the control panels 2 is in radio communication with a series of associated fire detectors 3 arranged in a series of zones 4. Each detector 3 has an associated radio transmitter (not shown) so that the detectors 3 of each zone 4 can transmit radio frequency signals to the associated control panel 2, i.e. the detectors 3 of each zone 4 transmit to a single control panel 2 in normal operation of the system.

Each of the control panels 2 is designed to communicate with the detectors 3 in its associated zone 4 independently of the other control panels 2. The control panel CPO is also in radio communication with each of the other control panels 2 to enable

the control panels 2 to exchange alarm and status data with each other, in a manner which will be described in greater detail below. This enables a failure or alarm condition of one control panel 2 or detector 3 to be communicated to a control panel 2 of another zone 4. For example, if the zones 4 of the system 1 represent different buildings, a control panel in one building in which no alarm condition exists can be notified of a fire in another building.

Referring now to Figure 2, communication between the detectors 3 and control panels 2 occurs by means of successive timing cycles 10, wherein each main timing cycle 10 consists of a series of sub periods 11. The sub periods 11 are in turn divided into individual timing cycles 12, each of which is divided into individual time slots, typically of 75 ms duration. These individual time slots include a broadcast slot 13 in which a synchronization signal is broadcast by one or more of the control panels 2 (in the example shown in Figure 1, this will be control panel CPO, since it can communicate directly with each of the other control panels) to all of the other control panels 2 and detectors 3 in the entire system 1 to enable those other control panels 2 and detectors 3 to synchronize their operation to each other. This enables internal timers of those devices to be arranged so that the transmitters of no two detectors 3 in the same zone 4 transmit simultaneously, which in turn avoids signal clashing. When a control panel 2 is not transmitting, it is in a receive mode during the broadcast slot 13 to receive broadcast signals from other control panels 2 which may be transmitting.

The broadcast slot 13 is followed by an alarm slot 14, which is used by control panels 2 for the reception of any alarm signal generated by any of the detectors 3 within the same zone 4 as the receiving control panel 2. As was the case with the

-8- broadcast slot, control panels 2 are always set to a receive mode during the alarm slot 14 in order to detect alarm signals.

An auxiliary slot 15 for distributing system information, update bulletins and the like follows the alarm slot 14. The auxiliary slot 15 is also used for transmitting an alarm signal from one of the control panels CP1 to CP4 to the central control panel CPO, which is in a receive mode for the auxiliary slot 15 of each timing cycle.

The auxiliary slot 15 is then followed by a control/acknowledgement slot 16 for sending an acknowledgement signal to a detector 3 in response to generation of an alarm signal by that detector 3. This enables the detector 3 to switch off or otherwise cease to generate an alarm signal after the alarm signal has been communicated to the associated control panel 2.

A status slot 17 for each timing cycle 12 follows the control slot 16 and enables a single detector 3 to report its status (i.e. functioning correctly or not) to the associated control panel 2. The status slot 17 is followed by a multi panel slot 18, which is used to distribute information between control panels 2. For example, an alarm or fault condition, resulting in the generation of a signal by a detector 3 in one zone 4, may be communicated to a control panel 2 in another zone 4.

This enables personnel in that other zone (by means of a suitable display device at the control panel 2 in that zone 4) to become aware of an alarm or fault situation in the other zone 4. Also, the control panel CPO, having received an alarm signal during an auxiliary slot 15, transmits that alarm signal onwards to other control panels CP1 to CP4 during the multi panel slot 18.

i: -9- In operation, a timing cycle 12 exists for each detector 3 in the system, and a sub period 11 consists of a series of timing cycles 12 in which each control panel 2 communicates with a single associated detector 3. The sub periods 11 are repeated for different detectors 3, and the number of sub periods 11 in each main monitoring period 10 is sufficient to enable each detector 3 in the system 1 to communicate with its associated control panel 2 If one of the detectors 3 should detect a fire, however, the detector 3 transmits an alarm signal to its associated control panel 2, which then activates a telephone dialler to notify the fire brigade, and may also automatically close fire doors. If the associated control panel is, for example, CP1, CP1 then transmits the alarm signal to the central panel CPO in its auxiliary slot 15. The central control panel CPO then transmits the alarm signal to the other control panels CP2 to CP4 in the associated multi panel slot 18. Because the central control panel CPO transmits the alarm signal simultaneously to the other control panels CP2 to CP4, not only is the alarm condition communicated to the other control panels much more rapidly than in the case of successive (i.e. non-simultaneous) transmission between control panels, but cumulative timing errors arising from such successive transmission are avoided.

Referring now to Figure 4, normal synchronization of the control panels 2 of Figure 1 is shown. In normal operation, the control panels 2 synchronize to the central control panel 2 of the system 1. In the arrangement of Figure 1, therefore, panel CPO issues a broadcast signal, and all other panels CP1 to CP4 synchronize to it (Figure 4a). In Figures 4b to 4e, if any of the other panels CP1 to CP4 issues a broadcast signal, since all of the panels 2 are synchronized, no panel 2 synchronizes to that broadcast signal.

-10 Referring now to Figure 5, if the control panels 2 are synchronized but for some reason the broadcast frame from panel CPO is not detected (as shown in Figure 5a), the timer in panel CPl is allowed to run and indicates when it is time to send its broadcast signal. Panel CPl then sends its broadcast signal and panel CP2 synchronizes to it (Figure 5b). Panel CP2 then sends its broadcast signal and panel CP3 synchronizes to it (Figure 5c) and panel CP3 sends its broadcast signal and panel CP4synchronizes to it (Figure 5d). If panel CPO then is reset, it wakes up into a detect mode in order to detect current broadcast packets to which it may re-synchronise itself, and synchronizes from panel CP3. As shown in Figure 4e, panel CP4 then sends its broadcast signal, but no other panels synchronize to it. Finally, as shown in Figure 4f, all panels 2 then synchronize to panel CPO since synchronization always occurs with the central panel if possible.

It will be appreciated by persons skilled in the art that the above embodiment has been described by way of example only, and not in any limitative sense, and that various alterations and modifications are possible without departure from the scope of the invention as defined by the appended claims.

Claims

A radio frequency alarm communication system comprising: a plurality of control units, wherein a plurality of first said control units are adapted to communicate by radio with a second said control unit; at least one respective signal input device associated with each said control unit, for generating an alarm signal in an alarm situation; and a respective radio transmitter for transmitting the or each said alarm signal from the or each said signal input device by radio to the associated control unit; wherein said control units are adapted to operate independently of each other and the timing of transmission of said transmitters associated with a said control unit is arranged such that simultaneous transmission of signals by more than one transmitter to a single control unit is prevented, and said second control unit is adapted to receive an alarm signal from a said first control unit and transmit said alarm signal directly to the or each other said first control unit.
2. A system according to claim 1, wherein at least one said control unit is adapted to transmit data to at least one other said control unit.
3. A system according to claim 2, wherein said data includes a timing signal to synchronize operation of a plurality of said control units.
4. A system according to claim 2 or 3, wherein said data includes an indication of the status of said control unit.

-12
5. A system according to any one of the preceding claims, wherein a plurality of said transmitters are adapted to transmit data relating to the associated signal input device to the corresponding control unit.
6. A system according to claim 5, wherein said data includes data relating to the status of said signal input device.
7. A system according to any one of the preceding claims, wherein at least one said control unit is adapted to transmit a timing signal to the or each said transmitter associated therewith to synchronize operation of the timing of said transmitters.
8. A system according to any one of the preceding claims, wherein said second control unit is the control unit capable of radio communication with -the largest number of said first control units.
9. A system according to any one of the preceding claims, wherein in the event of failure of said second control unit, the system is adapted to transmit a said alarm signal to said first control units by sequentially transmitting said signal between said first control units.
10. A system according to any one of the preceding claims, wherein at least one said signal input device is a fire and/or smoke detector.
11. A system according to any one of the preceding claims, wherein at least one said signal input device is an alarm communication device.
12. A system according to any one of the preceding claims,

-13 further comprising at least one alarm sounder for producing an audible alarm signal, said sounder being associated with a said control unit and adapted to be actuated by means of an actuation signal from the associated control unit.
13. A system according to claim 12, wherein at least one said alarm sounder is adapted to receive electrical power intermittently according to a signal from the associated control unit.
14. A system according to any one of the preceding claims, wherein the system in use carries out successive timing cycles in which each said transmitter sends a signal to the associated control unit.
15. A radio frequency alarm communication system substantially as hereinbefore described with reference to the accompanying drawings.
16. A radio frequency alarm communication method comprising: generating an alarm signal in an alarm situation; transmitting said alarm signal by radio directly to an associated control unit, wherein a plurality of first said control units are adapted to communicate by radio with a second said control unit, said control units are adapted to operate independently of each other and the timing of transmission of said alarm signal is arranged such that simultaneous transmission of more than one said alarm signal to a single said first control unit is prevented; if the associated said control unit is a said first control unit, transmitting said alarm signal directly by radio to said second control unit; and

-14 transmitting said alarm signal from said second control unit directly to the or each other said first control unit.
17. A method according to claim 16, further comprising the step of transmitting data from at least one said control unit to at least one other said control unit.
18. A method according to claim 17, wherein said data includes a timing signal to synchronism operation of a plurality of said control units.
19. A method according to claim 17 or 18, wherein said data includes an indication of the status of said control unit.
20. A method according to any one of claims 16 to 19, further comprising the step of selecting said second control unit such that said second control unit is the control unit capable of radio communication with the largest number of said first control units.
21. A method according to any one of claims 16 to 20, further comprising the step of transmitting a said alarm signal to said first control units by sequentially transmitting said signal between said first control units in the event of failure of said second control unit.
22. A radio frequency alarm communication method substantially as hereinbefore described with reference to the accompanying drawings.