An addressable alarm system

Abstract: An addressable fire alarm system comprises a plurality of heat and/or smoke sensors 10 connected to a control panel 13. The sensors 10 are programmed with their unique address codes by successively activating them using a heat or smoke source, the control panel 13 being arranged to transmit successive address codes to respective sensors 10 as they are successively activated. Each sensor 10 receives and stores its unique address code that is received from the control panel 13. The address code of each sensor 10 is thus very straightforward to set. Moreover, the system makes it easier to group the location of the sensors 10 according to their address codes.

Description: This invention relates to an addressable fire alarm system. Alarm systems are known which comprise a plurality of sensors connected to a cable which extends from a control panel. In use, the control panel is arranged to activate an alarm when one of the sensors detects an alarm condition. It is often desirable to be able to detect which of the sensors has been activated. Furthermore, it is often desirable to independently control and/or inhibit individual sensors. European patent application No. 0 191 239 discloses an addressable alarm system in which each of the sensors has a unique address code, so that the control panel can address one or more of the sensors and so that the control panel can recognise which sensor has been activated. Typically, each sensor comprises a plurality of switches which are set to give it a unique binary address code. A disadvantage of this arrangement is that it is complicated for alarm engineers to understand and set these binary codes. In order to overcome the above-mentioned problems, EP 0 734 005 discloses an addressable fire alarm system comprising a plurality of sensors arranged to transmit an alarm signal when activated by smoke or heat, and a control circuit arranged to monitor for a signal from the sensors in an address mode of the circuit and to transmit successive address codes to each sensor as they are successively activated, each activated sensor comprising means for receiving and storing said transmitted address code. In use, the control circuit is set to its address mode and the first sensor is activated. The control circuit detects that a first sensor has been activated, whereupon it transmits a first address code to the activated sensor. The activated sensor receives and stores the address code. The second sensor is then activated whereupon the control circuit transmits the next address code to the activated sensor. This process is repeated until all of the sensors have been given an address code. It will be appreciated that it is very straightforward for the alarm engineer to set the address code of each sensor. The alarm engineer is able to chose which sensor receives which address code merely be activating the sensors in the desired order. This has the advantage that the location of the sensors can be grouped according to their address code. US 4 855 713 discloses an addressable security alarm system in which the control circuit will only respond to sensors having a recognised address code. The control circuit is programmed with the address codes of the sensors to be recognised by causing a tamper alarm condition at each sensor in an address mode of the system. We have now devised an addressable alarm system of the type disclosed in EP 0 734 005 which is characterised in that the control circuit is arranged to transmit an address code to a sensor activated in response to an alarm signal generated by applying heat or smoke thereto. Thus, in order to set the address codes, the engineer merely has to activate the sensors by applying heat or smoke as appropriate. It is well known to provide aerosol cans of smoke for testing fire alarms and it will be appreciated that these provide a convenient means for activating the sensors during setting of their address code. The sensors are cheap to manufacture since additional sensing circuitry and switches of the type used in EP 0 734 005 are not required. The system merely relies on each sensor transmitting an alarm signal caused by the application of heat or smoke as a request for an alarm code, in the address mode of the system. Preferably each sensor is arranged to receive and store its address code within a predetermined time after an alarm condition has been detected. Preferably each sensor is arranged to transmit its stored address code together with said alarm signal when an alarm condition is detected in a standby mode of the circuit, so that the control circuit can determine which sensor has been activated. Preferably each sensor is arranged to emit a signal to indicate that an address code has been received and stored: in this manner the alarm engineer knows that he can move onto the next sensor. Preferably each sensor is arranged to transmit an acknowledgement signal to the control circuit to indicate that it has received and stored its address code, the control panel preferably being arranged to increment to the next address code upon receipt of said acknowledgement signal. Also, we have now devised a method, of the type disclosed in EP 0 734 005, of programming sensors of an addressable fire alarm system with address codes which is characterised in that the sensors are successively activated by applying heat or smoke thereto. An embodiment of this invention will now be described by way of example only and with reference to the accompanying drawing, the single figure of which is a block diagram of an addressable alarm system in accordance with this invention. Referring to the drawings, there is shown an addressable alarm system comprising a control panel 13 and a plurality of combined detector and sounder devices 10 connected in parallel across a pair of wires 11,12 having their opposite ends connected to the control panel. A plurality of manual call points 14 are also connected in parallel across the wires 11,12. The control panel 13 comprises a switch 15 which can be closed to place the control panel in an address mode. Each detector/sounder device 10 comprises a memory for storing its address. The devices 10 are preferably supplied with their addresses set to a default value, such as zero. Each device 10 comprises a smoke sensor and a heat sensor mounted in an airway e.g. 16. In use, the control panel 13 is set in the ADDRESS mode by closing the switch 15. The engineer installing the alarm then moves to the location of the device 10 that he wants to be at address No. 1, whereupon he activates the device either by spraying smoke into the airway from an aerosol or by using a heat gun. The activated device 10 then outputs a digital alarm signal onto the wires 11,12, the signal comprising an alarm code and the default address code of the device. The control panel 13 detects the digital alarm signal and recognises the alarm code, whereupon it applies a digital address signal onto the wires 11,12. The address signal comprises the first address code taken from an internal stack register. The devices 10 are arranged to enter a PROGRAM mode for a short period after they have been activated. Accordingly, the activated device 10 receives and decodes the digital address signal transmitted by the control panel and applies the decoded address code to its memory, in place of the default code. Once the device 10 has received and stored its address code it preferably outputs an audible acknowledgement signal to the engineer, so that he knows that he can proceed to the next device 10 to be set. The device 10 also applies a digital acknowledgement signal onto the wires 11,12. The control panel 13 detects the digital acknowledgement signal and increments to the next location in its stack register. The process is then repeated until all of the devices 10 have been assigned a unique address code from the stack register. The control panel 13 is then returned to its STANDBY mode by closing the switch 15. If a digital alarm signal is detected by the circuit 13 in STANDBY mode, it applies a digital warning signal to the wires 11,12. The control panel 13 is able to detect which device 10 has been activated, owing to digital alarm signal containing the address of the activated detector. Thus, the control panel 13 may apply a global or local warning signal to the wires 11,12 depending on how it is programmed to respond to the device 10 that is activated. Each device 10 monitors the wires 11,12 and responds to digital signals that contain its address code or global digital signals. In this manner, a plurality of devices 10 on a single pair of wires can be individually controlled, activated, tested and inhibited etc.

Claims: An addressable fire alarm system comprising a plurality of sensors (10) arranged to transmit an alarm signal when activated by smoke or heat, and a control circuit (13) arranged to monitor for a signal from the sensors (10) in an address mode of the circuit (13) and to transmit successive address codes to each sensor (10) as they are successively activated, each activated sensor (10) comprising means for receiving and storing said transmitted address code, characterised in that the control circuit (13) is arranged to transmit an address code to a sensor (10) activated in response to an alarm signal generated by applying heat or smoke thereto. An addressable fire alarm system as claimed in claim 1, characterised in that each sensor (10) is arranged to receive and store its address code within a predetermined time after said alarm condition has been detected. An addressable fire alarm system as claimed in claims 1 or 2, characterised in that each sensor (10) is arranged to transmit its stored address code together with said alarm signal when an alarm condition is detected in a standby mode of the circuit (13). An addressable fire alarm system as claimed in any preceding claim, characterised in that each sensor (10) is arranged to emit a signal to indicate that it has received and stored an address code. An addressable fire alarm system as claimed in any preceding claim, characterised in that each sensor (10) is arranged to transmit an acknowledgement signal to the control circuit (13) to indicate that it has received and stored its address code. An addressable fire alarm system as claimed in claim 5, characterised in that the control circuit (13) is arranged to increment to a next address code upon receipt of said acknowledgement signal. A method of programming sensors (10) of an addressable fire alarm system with address codes, comprising successively activating the sensors (10) whose addresses are to be set, monitoring, at a control circuit (13), for a signal transmitted by an activated sensor (10) and transmitting successive address codes to respective sensors (10) as they are successively activated and receiving and storing at the successively activated sensors (10), their respective address code received from the control circuit (13), characterised in that the sensors (10) are successively activated by applying heat or smoke thereto.

Inventors: AMLANI MANHAR, AMLANI, MANHAR
Applicants: RAFIKI HOLDINGS LTD, RAFIKI HOLDINGS LIMITED
Application year: 1998
Main classification: G08B26
IPC codes: G08B26