GB2451059A

GB2451059A - Analogue addressable alarm with two wire loop with specific alarm units directly triggered from detector units.

Info

Publication number: GB2451059A
Application number: GB0713098A
Authority: GB
Inventors: Steve Stringfellow
Original assignee: Computionics Ltd
Current assignee: Computionics Ltd
Priority date: 2007-07-06
Filing date: 2007-07-06
Publication date: 2009-01-21
Anticipated expiration: 2027-07-06
Also published as: GB0713098D0; GB2451059B

Abstract

An analogue addressable fire alarm system comprises a two wire loop 2 (see fig 1) carrying multiple alarm devices 3 including analogue addressable detectors and analogue addressable alarm sounders, the loop being connected to a control panel 1. In response to a detector, the control panel is able to trigger the sounders. Additional means may be connected between the loop 2 and an analogue addressable detector 3, the means able to produce an output 10 to trigger a selected one or more of the alarm devices when it is determined that a specific detector has sensed an alarm condition. This means is able to determine the address of the specific detector using control circuitry 9 connected to voltage 6 and current 8 sensing means attached to the loop. The means may include loop isolators.

Description

1 2451059

APPARATUS FOR A FIRE ALARM SYSTEM AND ASSOCIATED FIRE ALARM

SYSTEM

The invention relates to apparatus for an analogue addressable fire alarm system and to analogue addressable fire alarm systems incorporating such apparatus.

Addressable fire alarm systems are already well known. In such systems, a plurality of analogue addressable devices each having its own address, are wired across one pair of conductors formed in a loop and connected to fire alarm control equipment. These devices may be detectors such as fire or smoke detectors) or alarm devices such as visible alarms or fire alarm sounders. It is advantageous to provide system flexibility in which alarm devices in certain selected zones only of a building for example are activated when a particular detector device senses an alarm condition. This normally requires significant additional wiring which is both complex and expensive. One solution to this is described in GB 2276264A. In this solution the remote terminal output of an analogue addressable smoke detector is connected to an associated fire alarm sounder. Selected remote terminals are activated when a detector detects an alarm condition, in order to activate the corresponding sounders. However, this solution still requires appropriate alarm devices to be physically wired to corresponding remote terminals. It is an object of embodiments of the present invention to overcome this.

According to one aspect of the present invention there is provided apparatus for an analogue addressable fire alarm system said system having one or more analogue detectors and one or more analogue alarm devices and a control for controlling operation of the or each alarm device in response to signals received from the or each detector connected to a loop, said apparatus comprising means connected in operation to the loop and to the or each analogue detector for determining the address of a detector sensing an alarm condition and for activating a selected one or more of the alarm devices in dependence upon the detector identified.

According to another aspect of the present invention there is provided an analogue addressable fire alarm system comprising a loop, apparatus connected to the loop, one or more detectors connected to the apparatus, one or more alarm devices connected to the loop and control means for controlling the devices through the loop in response to signals from the detectors in which the apparatus comprises means for determining the address of an alarm detector sensing an alarm condition and for activating a selected one or more of the alarm devices in dependence upon the detector identified.

In a preferred embodiment of the invention, the means for determining the address comprises current sensing circuitry, voltage sensing circuitry and processing circuitry operative to receive signals from the current sensing circuitry and voltage sensing circuitry and to determine the address of the detector producing current signals. The apparatus has an output which is connected to an alarm device comprising a sonic transducer to generate an acoustic alarm signal. Advantageously, the apparatus comprises means for deriving power to drive itself from the analogue loop. An array of programming links may be provided enabling the apparatus to operate in any one of a number of different modes. For example, the apparatus may assume a fixed address or group of addresses relative to the protocol used and would not require any analogue device to be connected across the spur. Preferably, a loop isolator is provided enabling the apparatus to be isolated from the loop. Advantageously, monitoring means are provided for internal fault monitoring and switch means are provided responsive to the monitoring means enabling analogue devices connected to the spur to be disconnected. Such disconnection will generate a fault in the control when a disconnected device fails to respond to routine polling.

In order that the invention may be more clearly understood, embodiments thereof will now be described by way of example, with reference to the accompanying drawings, in which: Figure 1 is a block circuit diagram of a known analogue addressable fire alarm system, and Figure 2 is a block circuit diagram of an analogue addressable fire alarm system.

Referring to Figure 1, so called analogue addressable fire alarm systems are known (Figure 1) in which a multitude of addressable devices (3) are all wired across one pair of conductors forming analogue wiring (2) each device having an address. This single pair of conductors is normally wired in the form of a large loop back to a fire alarm control equipment (FACIE) (1). Loop isolators (4) are used to sense a short circuit on one section of the wiring and hence disrupt the "loop". This has the effect of isolating a section of the loop between loop S isolators and thus not causing total failure of the loop because of a single short circuit. These loop isolators are not germane to the invention but the device controller may contain one inbuilt for convenience.

Analogue addressable systems work by the FACIE (1) modulating the voltage on the analogue wiring (2) in a digital fashion in either the time or frequency domain. This series of messages are picked up by the analogue devices (3) and acted upon should the message be addressed to them individually. These particular analogue devices (3) then communicate with the FACIE (1) by returning a series of current pulses (in either the time or frequency domain) picked up by the FACIE (1), the information coded therein being then acted upon by the FACIE (1). The systems normally work in a half duplex mode with the master controller being the FACIE (1).

Since the returned current may be present in both parts of the "loop" analogue wiring (2) and is only summed at the FACIE (1) in order to be acted upon, and the master controller is the FACIE (1) then it follows that only the FACIE (1) knows physically which device (3) was being addressed and thus related to the current pulses. If it were possible to be able to identify the device (3) returning specific current pulses then it would be possible to deduce the address of the particular device (3), effectively eavesdropping on it. This would enable an unaddressed device to act on information being sent to an addressed device without any special connections to it. This device could be embodied and look as if it were another device type, for example it is known in analogue addressable systems that devices such as smoke detectors have a physical output that may be used to activate say a fire alarm sounder dependant on the programming of the FACIE (1).

Referring to Figure 2 an analogue addressable fire alarm system is shown modified in accordance with the invention in order to provide that facility. The system, which is shown in block circuit form, is referenced (5). Parts equivalent to parts of the arrangement of Figure 1 bear the same reference numerals. This system (5) contains voltage sensing circuitry (6) to extract in a digital manner the information being sent from the FACIE (1) down the loop wiring (2). Furthermore the device contains a spur output from the loop (13) which is effectively electrically the same as the loop wiring except it has a current sensing element (7) inserted in series with either the �ve or -ye leg, the increase in impedance introduced being very small in comparison with other line impedances thus becoming irrelevant in the correct functioning of the connected addressable devices (3). Only the current pulses generated by the device(s) 3 connected to the spur wiring (13) will generate a signal from the current sensing element. This signal is conditioned and information extracted in a digital manner by current analysis circuitry (8).

The digital signals from both the voltage (6) and current (8) sensing circuits are then sent to be processed to analysis and control processing circuitry (9). This circuitry is familiar with the analogue addressable protocol being used and since it is normal for only an addressed device to return current pulses it follows that circuitry (9) is able to deduce the address of the analogue addressable device (3) that is returning the pulses associated with the address being sent by the FACIE (1) and being detected by the voltage sensing circuitry (6).

Thus any analogue addressable devices (3) connected to the spur (13) can be eavesdropped on in this way. The outputs (10) from the analysis and control processing circuitry (9) via the output drive circuitry (14) may be in many forms dependant on the functioning of the system (5).

In one form output drive circuitry (14) drives a sound transducer (10) thus generating an acoustic alarm signal. The system includes means (11) for deriving the power it requires to drive itself from the loop (2). An array of programming links (16) are provided so that the system may operate in any one of a number of different modes. For example, the system (5) may assume a fixed address or group of addresses relative to the protocol used and would not require any analogue device (3) to be connected across its sense connections (13). A loop isolator (12) is also provided. The system is able to monitor for faults from within itself and trigger an internal switch (15) should such faults occur, thus disconnecting the analogue device(s) (3) connected to the spur output (13). This will result in a fault being generated at the FACIE (1) when disconnected device (3) fails to respond to routine polling.

Several devices (3) may be connected to the spur wiring (13), in which case the system (5) will be enabled to eavesdrop on these several devices.

The above described system enables selected analogue devices to be activated from an analogue detector without any direct physical connection between the detectors and devices. This in turn enables larger remote devices to be made such as wall mounted sounders. Monitoring of wiring is maintained and expensive programming switches (DIP switches) are not needed.

It will be appreciated that the above embodiments have been described by way of example only and that many variations are possible within the scope of the invention.

Claims

1. Apparatus for an analogue addressable firm alarm system, said system having one or more analogue detectors and one or more analogue alarm devices and a control for controlling operation of the or each alarm device in response to signals received from the or each detector connected to a loop, said apparatus comprising means connected in operation to the loop and to the or each analogue detector for determining the address of a detector sensing an alarm condition and for activating a selected one or more of the alarm devices independence upon the detector identified.

2. An analogue addressable firm alarm system comprising a loop, apparatus connected to the loop, one or more detectors connected to the apparatus, one or more alarm devices connected to the loop and control means for controlling the devices through the loop in response to signals from the * S.* detectors in which the apparatus comprises means for determining the *... 15 address of an alarm detector sensing an alarm condition and for activating a selected one or more of the alarm devices independence upon the detector identified.

S

**SSS.

*

3. A fire alarm system according to claim 2 wherein said determining the address comprises current sensing circuitry, voltage sensing circuitry and processing circuitry operative to receive signals from the current sensing circuitry and voltage sensing circuitry and to determine the address of the detector producing current signals.

4. Apparatus according to claim 2 or claim 3 which comprises an output which is connected to an alarm device comprising a sonic transducer to generate an acoustic alarm signal.

5. Apparatus according to any one of claims 1 to 4 further comprising means for deriving power to the drive itself from the analogue loop.

6. Apparatus accordingly to any one of claims 1 to 5 wherein an array of programming links are provided which allow the apparatus to operate in any one of a number of different modes.

7. Apparatus accordingly to claim 6 wherein the apparatus assumes a fixed address or a group of addresses relative to the protocol used thereby removing the need for connection of an analogue device across the spur.

**::*

8. Apparatus accordingly to any one of claims 1 to 7 wherein a loop isolator is provided to enable to apparatus to be isolated from the loop.

*..

9. Apparatus accordingly to any one of claims I to 8 further comprising monitoring means for internal fault monitoring and switch means which is responsive to the monitoring means enabling analogue devices connected * to the spurto be disconnected.

10. Apparatus substantially seen before described with reference to figure 2 of the drawings.