GB2288263A - Detection system and method - Google Patents

Description

2288263 Detection System and Method of Operating Same.

The present invention is detection systems comprising a multiplicityof detectors. The invention includes a method of operating such a detection system. The system and method are particularly suitable for detecting fires but may be used, suitably adapted, for detecting other eventualities, such as or other events threatening the security of a location.

Detectors which operate to give warning of the existence of conditions signifying a fire for example are widely used, either singly or as a group of detectors spread around the site protected by them. Single detectors may give direct audible little value unheard. it signals from a at a central possible to intrusions concerned with signal but such a signal on an extensive site and a may be of may pass is therefore usual for the warning group of detectors to be received control unit, at which it is respond quickly to any signal received.

Conventionally, such signals to a central location are passed by a direct line. The installation of a number of lines for this purpose may prove to be a relatively expensive exercise and in addition may be inconvenient or undesirable in some situations, for example where architecturally sensitive buildings or structures of historical significance are involved. In such situations at least, it is preferred to pass signals from detectors to a central control by radio.

A very limited number of radio-linked detection systems are available and in such systems, signals may be generated at a detector in two ways. Either the signal is a direct response to the occurrence of an incident, for example the onset of fire conditions or the presence of a fault in the detector, or the signal is produced as a matter of routine at a predetermined interval, for example to verify that the detector is functioning correctly. it may be a statutory requirement or a strong recommendation that such latter verification signals be transmitted, say, every half-hour or i t every few minutes.

Where there are a significant detectors monitored by radio from control unit, signals from two or more detectors may be transmitted at overlapping times, although the intention is that the signals should not overlap. The difficulty is that the timing of the individual transmissions becomes increasingly critical as the number of detectors and/or the planned frequency of verification increases, with the result that the accuracy of the individual timers controlling the individual detectors becomes a more important factor.

Timers of adequate accuracy over a prolonged period are not readily available; the timing achievable by available timers which are otherwise suitable for the purpose tends to drift over a period.

if such signals overlap, then the messages conveyed by the signals may become confused or may be lost or the signals may be interpreted wrongly.

It is therefore an object of the present invention to provide a fire detection system, and a method of operating such a system, by which the number of a central disadvantages of available such systems using multiple detectors are reduced or eliminated.

The detection system according to the present invention comprises a number of detectors for fire or other eventualities, each detector including a radio receiver, a radio transmitter and a timer adapted to determine the timing of the operation of said receiver and of said transmitter, and a monitoring unit adapted to transmit to each detector a synchronisation signal whereby the operations of said timers are co-ordinated and to receive signals from said detectors in predetermined sequence.

The method according to the invention of operating a detection system comprising a number of detectors each including a radio receiver, a radio transmitter and a timer, comprises transmitting to said detectors synchronisation signals to co-ordinate the operations of said timers and receiving and monitoring, in predetermined sequence, signals from said detectors.

Thus, by means of the detection system and method according to the present invention, each detector may send its required signal, f t f or example an " OK " signal verif ying that the detector is functioning properly, only in its own, unique time-slot, at the time set by its timer, which is synchronised by the signals from the monitoring unit. In this way, only one verification signal or the like is transmitted at a time and overlap of such routine signals is completely avoided.

The transmission of "emergency" signals, for example a fire warning, is performed in the same way, that is, in time-slots reserved for alarm signals, so interference between such signals is thereby avoided. Preferably, upon receipt of any transmitted information from a detector, the monitoring unit transmits to the of the for such detector an acknowledgement of receipt information, in a time-slot reserved acknowledgements.

The operation of a receiver at the site of each detector requires a source of power to enable the detector to receive and transmit signals. While that power may be provided from the mains electrical supply, it is convenient and simplifies installation of the detectors, for them to be powered by batteries, which may advantageously be of a "long-life" type. It is not necessary f or the receiver to operate continuously, ready to receive synchronisation signals from the monitoring unit; such continuous operation would require an unduly high consumption of power and would, in the case of a battery, greatly limit its operating life. The provision of a timer at each detector allows the receiver to be switched on just before it is due to receive a signal and to be switched off after the signal has been received, and for the transmitter to be operated only at the time when it is due to transmit a message. In one preferred form of the invention, a signal transmitted from the monitoring unit at predetermined intervals includes a check signal whereby the local timer is brought into alignment with the required timing sequence if it has departed from it.

The invention will by way of example the accompanying preferred embodiment system according and wherein:- one to 1 now be further described, only, with reference to illustrate detection invention drawings, which of the the present k - 7 Fig. 1 illustrates a simplified version of the system, comprising just two control panels and associated detectors; Fig. 2 is a representation of detector; and Fig. 3 illustrates a typical sequence of time-slots allocated for the transmission of specific forms of signal.

The illustrated detection system is based upon just two monitoring units in the form of control panels 11, 12 but may readily include several control panels, depending essentially upon the total number of detectors in the system. In the illustrated system, three detectors 13, 14, 15 are associated with control panel 11 and three detectors 16, 17, 18 are similarly controlled by control panel 12.

An alarm sounder 19 is associated with control panel 11 and two further alarm sounders 20, 21 are associated with control panel 12.

arrows in Fig. 1 represent radio links as shown, signals can be sent and received The and schematic a single 8 - in both directions between each of the control panels and its associated detectors and sounders, and also between the control panels.

Each of the detectors 13 to within it four components, as schematically in Fig. 2. Thosecomponents are a radio signal receiver 22, a transmitter 23, a timer unit 24 and a battery 25 which provides the electrical power for the other three components. The receiver 22 is designed receive radio signals transmitted by the control panel with which it is associated, while" the transmitter 23 is designed to send signals to the control panel, either interval to report the in a time-slot purpose., to example to radio at a status predetermined of the detector or, reserved for that "alarmtl condition (for intruder) detected by a sensor in the detector.

The transmission of signals of all types between the various illustrated units is governed to follow a strict sequence of time slots controlled by the control units in cooperation with the timer units 24. That is, in the 18 includes represented indicate an f ire or an (not shown) g - 9 system overall, each type of signal, for example status-reporting signals, alarm signals and signals confirming the receipt of transmitted information, is consigned a specific short time slot or several time slots within which it may be transmitted. Each timer unit 24 controls the timing of those time-slots in sequence and the synchronising of the operation of the timer units 24 is controlled by the regular transmission of a common time reference signal (called in this example the "broadcast" signal) by the control units 11, 12 to their associated detectors or, preferably, by a master panel (not shown).

A typical sequence of time slots is illustrated in Fig. 3, which is a plot of signal slots against time, in the direction of the arrow. Time slots bearing the letter 'B' are the slots reserved for the transmission of the synchronising "broadcast" signal. Time slots 'C' are for signals between control panels. The time slots identified by the letter 'S' are dedicated to signals from the detectors reporting their status at predetermined intervals, for example that the individual - 10 detector is operating satisfactorily or requires attention. Finally, time slots W are reserved for alarm signals. Power from the battery to the receiver 22, to enable it to receive acknowledgement is provided the receiver the "broadcast" signal or an of a signal previously transmitted only in those time slots in which is required to operate.

As will be apparent from the description, the detection system and according to the present invention make possible for a multiplicity of detectors to be monitored by radio from a central control position without the potential for conflict of signals which is a feature of presently available such systems. The detectors may all be associated with the same monitoring such units may be provided, 1 unit and each the detectors, synchronisation a further advantdetection systems so controlled that ls from the adjacent unit or several each synchronised by a centra associated with several of thereby achieving overall of all of the detectors. As ageous possibility, adjacent in nearby locations may be potential conflict of signa systems is also avoided.

1 Q foregoing method it

Claims (10)

1. A detection system comprising a number of detectors for fir.e or other eventualities, each detector including a radio receiver, a radio transmitter and a timer adapted to determine the timing of the operation of said receiver and of said transmitter, and a monitoring unit adapted to transmit to each detector a synchronisation signal whereby the operations of said timers are coordinated and to receive signals from said detectors in predetermined sequence.

2. A detection system as claimed in Claim 1, wherein each detector further includes a source of electrical power.

3. A detection system as claimed in Claim 2, wherein said source of electrical power is a battery.

4. A detection system as claimed in any of the preceding claims, which further comprises at least one alarm sounder.

5. A detection system as claimed in any of the preceding claims, comprising at least two said monitoring units, each associated with several said detectors, and a central unit adapted to synchronise 12 - the operation of said monitoring units and detectors.

6. A method of operating a detection system which comprises a number of detectors each including a radio receiver, a radio transmitter and a timer, which method comprises transmitting to said detectors synchronisation signals to coordinate the operations of said timers and receiving and monitoring, in predetermined sequence, signals from said detectors.

7. A method as claimed in Claim 6, wherein the signals of different types are alloted different time-slots in a repeated sequence of time-slots.

8. A method as claimed in either of Claims 6 and 7, including the step of acknowledging the receipt of signals from said detectors.

9. A method as claimed in any of Claims 6 to 8, wherein electrical power is provided for each said receiver and transmitter only at times when said receiver or transmitter is required to receive or transmit a signal.

10. A detection system substantially as hereinbefore described with reference to, and as illustrated in, the accompanying drawings.

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