Abstract:
An interface circuit of a sub-system of a distributed fire detection system having a plurality of sub-systems, wherein the plurality of sub-systems are in communication with each other in a loop configuration to allow data signals to be routed between said sub-systems. The interface circuit connects the internal components of a sub-system to the external bus line connecting all components via at least three input/output ports. It comprises hardware logic components, namely switches and switch controllers listening for incoming data and opening or closing said switches to cause disconnection and connection between said input/output ports accordingly, thereby allowing the routing of data signals to one or more of the other input/output ports. The simpler configurations replaces a routing processor.

Description:
FIELD OF THE INVENTION 
       [0001]    The invention relates to an interface circuit and, in particular, to an interface circuit for a sub-system of a fire detection system. The invention also relates to a sub-system of a fire detection system. 
       BACKGROUND OF THE INVENTION 
       [0002]    Modern detector systems, such as fire detection systems, intruder detection systems, and flood detection systems include a number of detectors which are connected to a common wired network together with a central control unit. For example, in a fire detection and alarm system, the central control unit, such as a fire alarm control panel (or commonly referred in the art as a Control and Indicating Equipment (CIE)), has a number of detectors connected to it in a loop. The detectors are located throughout a premise to detect changes associated with fire. 
         [0003]    As illustrated in  FIG. 1 , a known fire detection system  10  has a CIE  12 , a plurality of detectors, labelled S 1  to S n . and control line  14  connecting, the CIE  12  to the detectors. The control line  14  forms a single loop, beginning and ending at the CIE  12 . In this example, the system  10  has only one loop, but it will be appreciated that the system might have a plurality of loops, each loop connecting a plurality of detectors to the CIE  12 . 
         [0004]    As shown in  FIG. 2  another known fire detection system  20  may have one or more CIEs  30 ,  40 ,  50  distributed in a monitored area Referring to  FIG. 2 , each of the CIEs, for example CIE  30 , in the system comprises at least two Input/Output (I/O) terminals  30   a,    30   b  to allow the CIE  30  to be connected, by means of data buses  32 ,  36  to other CIEs  40 ,  50  to faint a CIE communication network, so that information from a CIE can be relayed to another CIE through the network. Similarly, each of the CIEs has a plurality of detectors connected to it in a single loop (or multiple loops) as described in the preceding paragraph. 
         [0005]    A CIE of the fire detection system of  FIGS. 1 and 2  will now be described with respect to  FIG. 3 . 
         [0006]      FIG. 3  shows schematically the components of a CIE  12 . In this simplified illustration, the CIE  12  includes a Main Central Processing Unit (MCPU)  60 , a Loop Central Processing Unit (LCPU)  62 , and a User Interface (UI)  64 . For the sake of simplicity, only the MCPU  60 , LCPC  62 , and the UI  64  are illustrated in  FIG. 3 . However, it will be appreciated that the CIE  12  may comprise other components, such as memory, or data storage means. By means of an internal bus  66 , the MCPU  60 , LCPU  62 , and the UI  64  are in communication with each other, and other CIEs in the network. 
         [0007]    The primary function of the MCPU  60  is to control the overall operation of the CIE  12  including transmitting an alarm signal upon receiving a signal from the LCPU  62  indicating a fire. A plurality of detectors are connected to the LCPU  62  in a single loop so that in event of a fire, a detector can provide an alarm signal to the LCPU  62  which in turn provides a signal to the MCPU  60  so that a decision on what action to take can be made based on a predetermined sequence. Of course, multiple loops of detectors can be connected to the LCPU  62 . 
         [0008]    The CIE  12  also includes input/output terminals  68 ,  70  through which data signals can be transmitted to / received from another CIE. 
         [0009]    In the prior art, a routing processor is required to route data (or information) between the internal data bus  66  and an external data bus (not shown) in order to transfer data from/to a component of a CIE to another CIE in the network. The routing processor may be incorporated into one of the components of the CIE (for example, the MCPU) to control routing of data between the internal data bus and the external data bus. However, in the event that the routing processor fails, it will not be possible to route the data between the internal bus and the external data bus—resulting in communication failure. 
       SUMMARY OF THE INVENTION 
       [0010]    In a first aspect of the invention there is provided an interface circuit of a sub-system of a distributed fire detection system having a plurality of sub-systems, wherein the plurality of sub-systems are in communication with each other in a loop configuration to allow data signals to be routed between said sub-systems, the interface circuit comprising at least three input/output ports through which data signals can be received or transmitted, each of said ports being connectable to at least two of the other input/output ports to establish a connection therebetween, a plurality of switches, each switch arranged between a pair of the input/output ports to establish a connection, the switch having a closed position and an open position; and a plurality of sensors, each being coupled to a respective one of said input/output ports, and upon detection of said data signals the sensor is operable to generate a control signal to open or close at least one of said switches to cause disconnection and connection between said input/output ports, thereby allowing the data signals to be routed to one or more of the other input/output ports. This is advantageous in that the interface circuit allows routing of data between the sub-systems using hardware logic devices, without relying on a routing processor. 
         [0011]    Preferably, said switches are connected together in a loop, thereby allowing data signals to pass from one input/output port to any other input/output port of the interface circuit. 
         [0012]    The control signal is generated upon detection of a beginning of said data signals. 
         [0013]    Each of said sensors may comprise a first terminal and a second terminal, the first terminal being connected to said respective input/output port and the second terminal being connected to at least two switches. 
         [0014]    The interface circuit may be arranged between an internal data bus of said sub-system and at least two external data buses coupled with said sub-system, such that the interface circuit allows data communication between at least one component of said sub-system and another sub-system of said plurality of sub-systems. 
         [0015]    The interface circuit may be incorporated into a complex programmable logic device. 
         [0016]    In a second aspect of the invention there is provided a sub-system for a fire detection system, comprising an interface circuit according to the above aspect. 
         [0017]    The sub-system may further comprise a main central processing unit, a loop central processing unit, a user interface unit, and an internal data bus through which said units are in communication with each other and the interface circuit. 
         [0018]    The internal data bus may be in accordance with the RS 485 standard. 
         [0019]    In a third aspect of the invention there is provided a fire detection system comprising a sub-system according to the second aspect, and at least one further said sub-system arranged to communicate with each other via said interface circuit of the first aspect. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0020]    Embodiments of the invention will now be described with reference to the accompanying drawings, wherein; 
           [0021]      FIG. 1  illustrates an arrangement of a detection system according to the prior art; 
           [0022]      FIG. 2  illustrates an arrangement of a loop communication network according to the prior art; 
           [0023]      FIG. 3  illustrates a schematic representation of a prior art control panel; 
           [0024]      FIG. 4  illustrates an example of a distributed loop communication network according to an, embodiment of the invention; 
           [0025]      FIG. 5  illustrates a schematic representation of a sub-CIE according to an embodiment of the invention; and 
           [0026]      FIG. 6  illustrates a schematic representation of an interface circuit according to an embodiment of the invention. 
       
    
    
     DETAILED DESCRIPTION 
       [0027]    Specific embodiments of the invention will be described in further detail in the following description with reference to the attached figures. It will be appreciated that the embodiments are described by way of example only, and should not be viewed as presenting any limitation on the scope of protection. 
         [0028]    European standard, EN54, specifies requirements for all component parts of a fire alarm system. The EN54 standard also introduces a concept of distributed CIE (Control and Indicating Equipment), In simple terms, a distributed CIE allows components, such as the MCPU, LCPU, and UI that form a single CIE to be distributed in a number of independent “sub-CIEs” in the network, such that operation of the sub-CIEs in the network can be controlled by a single MCPU located in one of the sub-CIEs to allow a common global event or action in an event of a fire. 
         [0029]    An example of a distributed CIE system deployed in a monitored area is illustrated in  FIG. 4 . In this example, the distributed CIE network  100  is a collection of sub-CIEs  110 ,  120 ,  130 ,  140  having different components that together form the function of a CIE. 
         [0030]    The distributed CIE system  100  in  FIG. 4  includes four sub-CIEs  110 ,  120 ,  130 .  140  in communication with each other in a single loop configuration. Each sub-CIE includes a first I/O terminal  110   a,    120   a,    130   a,    140   a,  and a second I/O terminal  110   b,    120   b,    130   b,    140   b.  As shown in  FIG. 4 , the second I/O terminal  110   b  of sub-CIE  110  is connected to the first I/O terminal  120   a  of sub-CIE  120  via a data bus  118 . Similarly, the second I/O terminal  120   b  of sub-CIE  120  is connected to the first I/O terminal  130   a  of sub-CIE  130  via a data bus  128 . 
         [0031]    The second I/O terminal  130   b  of sub-CIE  130  is connected to the first I/O terminal  140   a  of sub-CIE  140  via a data bus  138 . Finally. the second I/O terminal  140   b  of sub-CIE  140  is connected to the first I/O terminal  110   a  of sub-CIE  110  via a data bus  148 . 
         [0032]    In this example, detectors are deployed in detector loops  116  by the sub-CIE  110  and the sub-CIE  140  by means of LCPU  112  and LCPU  142  respectively. 
         [0033]    A MCPU  132  located in sub-CIE  130  controls the overall operation of the distributed CIE system  100 . Sub-CIE  130  functions as a central monitoring and controlling unit that receives information from the LCPU  112  of sub-CIE  110  via data buses  118  and  128 , or data buses  148  and  138 , depending on the direction in which the data is routed. Sub-CIE  130  also receives information from the LCPU  142  of sub-CIE  140  via data bus  138 , or data buses  148 ,  118  and  128 . 
         [0034]    The MCPU  132  makes a decision on what action to take based on the received information, such as providing for automatic control of equipment, and transmission of information necessary to prepare the monitored area for fire based on a predetermined sequence. For instance, if a fire is detected by one of the detectors connected to LCPU  112 , a fire signal is reported from sub-CIE  110  through the distributed CIE network  100  to the MCPU  132  of sub-CIE  130 . Upon receiving the fire signal, the MCPU  132  interprets the information and, if appropriate, provides an alarm signal to a user interface (UI)  122  in sub-CIE  120 . As shown in  FIG. 4 , the UI  122  and MCPU  132  are in communication via the data bus  128 . 
         [0035]    The UI  122  includes user operable input devices such as a keyboard and a touchpad, but could include a mouse or other pointing device, a contact sensitive surface on a display unit of a computer terminal, or any other means by which a user input action can be interpreted and converted into data signals. The UI  122  allows the user to program the MCPU  132  by transmitting the converted data signals from the user&#39;s input to the MCPU  132 . The UI also includes output device(s) capable of providing an output signal according to a signal sent from the MCPU  132 . The output device may also include a display screen for presenting the user with a message describing the location of the alarm and the type of event (e.g. smoke, or heat). For example, when the UI  122  receives an alarm signal from the MCPU  132 , the UI  122  switches on a siren or relays the alarm signal to the fire brigade. 
         [0036]    It is noted that one of the requirements of a distributed CIE system is the ability to communicate between the distributed components of the CIE over more than one communication path. For example, if the data bus  118  is broken or disconnected, the MCPU  132  in sub-CIE  130  is still able to communicate with sub-CIE  110  via data buses  138  and  148 . 
         [0037]    The component(s) in a sub-CIE (e.g.  140 ) are connected to an internal bus  144  which is connected to the I/O terminals of the sub-CIE  140  to allow the components of the sub-CIE  140  to communicate with other sub-CIEs  110 ,  120 ,  130  in the network. As shown in  FIG. 4 , the internal bus  144  is split into two paths which are connected to I/O terminals  140   a  and  140   b.  It is noted that the I/O terminals  140   a,    140   b  are bidirectional. 
         [0038]      FIG. 5  illustrates a sub-CIE  200  of a distributed CIE system which is generally capable of establishing communication with one or more other sub-CIEs for data communication and, according to embodiments of the invention, of control routing of data between an internal bus  208  of the sub-CIE  200  and a pair of external buses  220 ,  222  connected to the sub-CIE  200 . 
         [0039]    The CIE  200  illustrated in  FIG. 5  comprises a Main Central Processing Unit (MCPU)  202 , a Loop Central Processing Unit (LCPU)  204 , and a User Interface (UT)  206 . In the present embodiment, the primary function of the MCPU  202  is to control the overall operation of the distributed CIE  100  including transmitting an alarm signal upon receiving a signal from a LCPU indicating fire. A plurality of detectors (not shown) is connected to the LCPU  204  in a single loop or in multiple loops so that in an event of a fire, a detector can provide an alarm signal to the LCPU  204  which in turn provides a signal to the MCPU  202  so that a decision on what actions to take can be made based on a predetermined sequence. 
         [0040]    Although it is illustrated in this example that the components of the sub-CIE  200  includes a MCPU  202 , a LCPU  204 , and a UI  206 , a skilled reader will appreciate that in a distributed CIE system network these components may be distributed in other locations (in other sub-CIEs) in the network. 
         [0041]    The components (MCPU  202 , LCPU  204 , and UI  206 ) of the sub-CIE  200  are connected to an internal bus  208  which allows data to be routed between the components and other distributed sub-CIE in the network. 
         [0042]    The sub-CIE  200  also includes a first I/O terminal  216 , and second I/O terminal  218 , both of which are bidirectional, and an interface circuit  210  operable to route data between the internal bus  208  and the external buses  220 ,  222  to enable communication of data between distributed sub-CIEs in the network. In this example, the internal data bus conforms to the RS 485 standard. 
         [0043]    As shown in  FIG. 5 , the interface circuit  210  comprises three input/output (I/O) ports  210   a,    210   b,  and  210   c.  I/O port  210   a  is connected to the internal bus  208 , I/O port  210   b  is connected to I/O terminal  216  of the sub-CIE  200  via internal bus  212 , and I/O port  210   c  is connected I/O terminal  218  of the sub-CIE  200  via to internal bus  214 . 
         [0044]    In this illustrated example, the interface circuit  210  comprises three I/O ports, but it will be appreciated that practical implementations may include more I/O ports depending on the application. An example of the interface unit is a programmable logic device, such as a Complex Programmable Logic Device (CPLD). Other suitable hardware devices also include an application specific device such as an ASIC or and FPGA, or other dedicated functional hardware means. 
         [0045]    One of the advantages of the invention is that it allows routing of data between internal and external data buses using hardware logic devices, without relying on a routing processor. 
         [0046]    An interface circuit for routing data between an internal bus of a sub-CIE and external data buses connected to the sub-CIE will now be described in more detail with respect to  FIG. 6 . The interface circuit implemented in a sub-CIE allows components of the sub-CIE and other sub-CIEs connected to it to communicate seamlessly with each other without the need for a routing processor to control communication between the internal and external data bus. 
         [0047]      FIG. 6  shows schematically components of an interface circuit  500 . The interface device  500  comprises first, second, and third input/output (I/O) ports  502 ,  504 ,  506 , first, second, and third sensors  508 ,  510 ,  512 , and first, second, and third switches  514 ,  516 ,  518 . 
         [0048]    Each of the sensors  508 ,  510 ,  512 , comprises two terminals, wherein one of the terminals is connected to an I/O port of the interface device  500  and the other terminal is connected to two switches. The switches  514 ,  516 ,  518  in the interface device  500  are connected together in a series loop. The switches  514 ,  516 ,  518  are controlled by control signals via control lines (not shown). Alternatively, the control signals are generated by the sensors  508 ,  510 ,  514 . 
         [0049]    In detail, the sensor  508  comprises a first terminal  508   a  and a second terminal  508   b.  The first terminal  508   a  is connected to the I/O port  502  through which communication can be established with an internal bus (not shown). The second terminal  508   b  is connected to a first terminal  514   a  of the switch  514  and a first terminal  518   a  of the switch  518 . A second terminal  514   b  of the switch  514  and a second terminal  518   b  of the switch  518  are connected respectively to a first terminal  516   a  and a second terminal  516   b  of the switch  516 , such that the switches  514 ,  516 ,  518  in the interface device  500  are connected together in a series loop. The second terminal  514   b  of switch  514  and the first terminal  516   a  of switch  516  are also connected to a first terminal  510   a  of the sensor  510 , and a second terminal  510   b  of the sensor  510  is connected to the I/O port  504 . Similarly, the second terminal  518   b  of terminal  518  and the second terminal  516   b  of switch  516  are connected to a first terminal  512   a  of the sensor  512 , and a second terminal  512   b  is connected to the I/O port  506 . 
         [0050]    Each of the sensors  508 ,  510 ,  512  is configured to detect the start of a data signal transmitted from one sub-CIE to another sub-CIE, and to generate a control signal to control the operation of the switches that are connected to a common connection point. For example, a sensor can be configured to detect a start bit of a data stream (or a header of a data packet) received at a respective I/O port of the interface device. It is noted that any suitable method of detecting the start of data transmission may be employed. For this reason, details of the sensor will not be further described. 
         [0051]    When sensor  508  detects a start bit of a data signal, it generates a control signal to close either switch  514  or switch  518 , depending on the direction in which the data signal is to be routed in the distributed CIE system. For example, upon detection of a start bit of a data signal coming through the interface device  500  at port  502 , the sensor  508  generates a control signal to close switch  514  such that the connection points  520  and  522  are connected to each other. Switches  516  and  518  remain open. In this configuration, data signals received from the internal components via I/O port  502  are directed to I/O port  504  and to an external data bus via sensor  508 , switch  514  and sensor  510 . In another example, the sensor  508  may generate a control signal to close switch  518  rather than switch  514 , so that data signals received from the internal components via I/O port  502  are directed to I/O port  506  to an external data bus via sensor  508 , switch  518  and sensor  512 . In this example, switches  514  and  516  remain open. 
         [0052]    However, when an external data signal is received via I/O port  504 , the sensor  510  generates a control signal to close switches  514  and  516 , and switch  518  remains open. In this configuration the data signal is directed to internal components of the sub-CIE through switch  514  via I/O port  502 . The data signal is also directed through switch  516  to an external data bus connected to I/O port  506 . This configuration may be appropriate, for example, in the sub-CIE  130  of  FIG. 4 . Referring to  FIGS. 4 and 6 , when a fire signal detected by a detector of the LCPU  142  of sub-CIE  140  is sent to sub-CIE  130  via external data bus  138 , the lire signal is directed to the MCPU  132  of sub-CIE  130  to inform the MCPU  132  that a fire has been detected. The fire signal is directed to the MCPU via I/O port  504 , switch  514 , and I/O port  502  of the interface circuit  500 . As the switch  516  of the interface circuit  500  is also closed, the fire signal can be relayed to another sub-CIE (in this example, sub-CIE  120 ), via I/O port  504 , switch  516 , and I/O port  506  of the interface circuit  500 . The fire signal that is relayed to sub-CIE  120  can be used to display a warning message via the UI  122  of sub-CIE  120 . 
         [0053]    In yet another example, the sensor  510 , upon detection of a data signal coming through the interface circuit  500  at port  504 , generates a control signal to close switch  516  such that the connection points  522  and  524  are connected to each other. Switches  514  and  518  remain open. In this configuration, data signals received via. I/O port  504  are directed to I/O port  506  and to an external data bus via sensor  510 , switch  516  and sensor  512 . This configuration can be implemented, for example, in the sub-CIE  120  of  FIG. 4 , so that the sub-CIE  120  simply acts as a relay to relay a fire detected signal from the LCPU  112  of sub-CIE  110  to the MCPU  132  of sub-CIE  130 . Referring to the set up in  FIG. 4 , when a fire signal is detected by the LCPU  112  of sub-CIE  110 , the fire signal is sent from the LCPU  112  of sub-CIE  110  to sub-CIE  120  via I/O port  110   b  and data bus  118 . Upon receiving the fire signal at I/O port  120   a,  the fire signal is immediately directed to I/O port  120   b,  and subsequently to the MCPU  132  of sub-CIE  130  via data, bus  128  and I/O port  130   a.    
         [0054]    In yet another example, when an external data signal is received via I/O port  506 . the sensor  512  detects a start bit of a data signal and generates a control signal to close switches  516  and  518 , and to set switch  514  in an open configuration. In such a configuration, the data signal entering the I/O port  506  is directed to internal components of the unit through switch  518  via I/O port  502 . The data signal is also directed through switch  516  to an external data bus connected to I/O port  504 . 
         [0055]    It will be appreciated by the person skilled in the art that although examples provided herein are directed to fire detection systems, the devices or circuits described can also be applied to any environmental detection system. For example, the described method can be applied to a flood detection system in a monitored area. 
         [0056]    While certain embodiments have been described, these embodiments have been presented by way of example only, and are not intended to limit the scope of the inventions. Indeed, the novel circuits, devices and systems described herein may be embodied in a variety of other forms; furthermore, various omissions, substitutions and changes in the form of the circuits, devices and systems described herein may be made without departing from the spirit of the inventions. The accompanying claims and their equivalents are intended to cover such forms or modifications as would fall within the scope and spirit of the inventions.