Abstract: The present invention relates to a fire detector testing device for installation with, or retrofitting to, a fire detector. An aerosol generator in fluid connection with a liquid reservoir directs an aerosol towards a detector element of the fire detector in order to test whether smoke entry has been compromised. The liquid reservoir of the present invention may be installed within a base of the detector, between the base and the detector, or in the detector itself.

Abstract: A fire detector system comprises a fire detector unit; a sensor disposed in the fire detector unit and arranged to detect the characteristics of a fire and to generate an output signal indicative of the characteristics detected by the sensor; and a processor arranged to receive the output signal from the sensor and to generate afire alarm signal when the output signal exceeds an alarm point threshold; wherein the system is arranged to change the alarm point threshold over time to compensate for drift in the response of the detector unit; wherein the fire detector unit includes a first sensitivity mode with a first drift compensation limit and a second sensitivity mode with a second drift compensation limit, the second sensitivity mode being more sensitive than the first; and wherein, as the first alarm point threshold in the first sensitivity mode is approached or reached, the mode of the system is changed to the second sensitivity mode.

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.

Abstract: An isolator circuit (25) for a unit of a safety system (10) includes a power control line (14) connectable to a first loop of a safety system and a power connection (16) connectable to a second loop of the safety system. A switch (26) is connected to the power control line (14), and the switch has a closed configuration and an open configuration. A controller (28) controls the configuration of the switch (26). If a voltage across the circuit (10) from the power connection (16) to the power control line (14) falls below a predetermined level, the controller (28) opens the switch (26), thereby causing a disconnection to occur in the first loop.

Abstract: A detector comprises a housing (1), a pyroelectric array sensor (2) mounted within the housing, a heater (4) associated with the pyroelectric array sensor, and control means (6) for varying the power supplied to the heater to control the temperature of the pyroelectric array sensor relative to the ambient temperature in order to minimise the rate of change of temperature of the pyroelectric array sensor and to keep a predetermined difference between the temperature of the pyroelectric array sensor and the ambient temperature.

Abstract: A nodal system (10) includes a unit (D) having a memory (42) and an optical data receiver (36), and a common control unit (12) in communication with the unit. A method of commissioning the system comprises the steps of activating the optical data receiver on the unit, and transmitting an optical data signal to the unit, thereby commissioning the unit.

Abstract: A particulate detector (10) comprises a radiation source (12) arranged to emit radiation in at least first and second predetermined wavebands towards a sampling region (18) suspected of containing particulates, and a detection element (14), shielded from the radiation source (12), and arranged to detect radiation from the sampling region (18) at least first and second instances. The radiation source (12) is such that the emissions in the wavebands temporarily overlap. The detector is such that, at the instances at which the radiation is detected, the relative contributions from the emissions in each predetermined waveband are distinguishable, thereby allowing characteristics of the particulates to be determined. The radiation source (12) may comprise a light emitting diode (24).

Abstract: A detector includes a component having a surface. The surface includes, or is at least partially coated with, a contaminant-resistant or self-cleaning material. This allows the detector to remain clean without manual cleaning.

Abstract: A method and apparatus of identifying a plurality of devices connected along a common communications link is disclosed. A control station scans the devices by sending a succession of interrogation signals along the communication link, the interrogation signals including representation of the identification numbers of the devices. A first scan is carried out with interrogation signals identifying a first level of the range of identification numbers, and each device is programmed to generate, and to send to the control station, a response signal that includes its complete identification number and a checksum, upon receipt of a scan signal applicable thereto. Successive scans are carried out by the control station, adding the next higher level or the range of identification numbers, wherein upon completion of the scan that does not give rise to valid responses, the previously-paused scan is resumed.

Abstract: A detector comprises a detector base and a sensor, first and second resistors connected in series, a DC voltage source (Vref) connected to the resistors, and means for monitoring the voltage at the midpoint of a potential divider constituted by the series-connected resistors. The first and second resistors are rated so that the midpoint voltage is indicative of the date of manufacture of the sensor.

Abstract: A particulate detector (10) comprises a radiation source (12) arranged to emit radiation in at least first and second predetermined wavebands towards a sampling region (18) suspected of containing particulates, and a detection element (14), shielded from the radiation source (12), and arranged to detect radiation from the sampling region (18) at least first and second instances. The radiation source (12) is such that the emissions in the wavebands temporarily overlap. The detector is such that, at the instances at which the radiation is detected, the relative contributions from the emissions in each predetermined waveband are distinguishable, thereby allowing characteristics of the particulates to be determined. The radiation source (12) may comprise a light emitting diode (24).

Abstract: A flame detector is provided which comprises a housing (1), a test source of electromagnetic radiation (4) and a sensor (7). The source of electromagnetic radiation (4) and the sensor (7) are mounted within the housing (1). The source of electromagnetic radiation (4) is arranged to direct its output onto the sensor (7). The source of electromagnetic radiation (4) is arranged to emit radiation which simulates a flame. In this way, a means is provided within the housing (1) of the flame detector to test the flame detector without the need for an external test source, such as a test fire or a bulky and expensive test torch.

Abstract: A detector comprises a housing (1) having a window (3), a measuring and processing unit (2), a source (4) of electromagnetic radiation, a plurality of sensors (7), and a reflector (6). The measuring and processing unit (2), the electromagnetic radiation source (4) and the sensors (7) are mounted within the housing (1). The reflector (6) is mounted outside the housing (1). The reflector (6) is positioned to reflect electromagnetic radiation passing through the window (3) from the electromagnetic radiation source (4) onto the sensors (7) via the window. The sensors (7) are operatively associated with the measuring and processing unit (2) to provide that unit with an input indicative of the level of electromagnetic radiation reaching the sensors.

Abstract: A self-monitoring smoke detector comprising a housing (11) defining an internal chamber (12). An optical transmitter (13) is mounted within the housing (11) so as to direct light into the optical chamber (12). An optical receiver (14) is mounted in the housing (11) and in optical communication with the optical chamber (12). The optical transmitter (13) and the optical receiver (14) are so positioned that light from the transmitter cannot directly reach the receiver. Monitoring means is provided, comprising first and second light-scattering means (13a and 14a) positioned respectively in alignment with the transmitter (13) and the receiver (14). The arrangement is such that, in the absence of reflector particles in the optical chamber, light from the transmitter (13) can reach the receiver (14) only after scattering at the first light-scattering means (13a) and then after scattering at the second light-scattering means (14a).

Abstract: A detection system in which a single sensor (14) is employed to detect two, or more, levels, or ranges, of a parameter. The output signal from the sensor (14) is fed to a detection circuit (12) for amplification and thence to a control circuit (24). The control circuit (24) is switchable, either manually, or preferably programmably, for example by a timer, between two or more modes of operation for processing the output signal from the sensor (14) in a different manner, for example using different algorithms, according to the condition that is to be detected. The switching of the control circuit (24) between its modes results in a signal being sent to the detection circuit (12) to change its sensitivity to the signal received from the sensor (14), thereby to maintain accuracy of measurement of the parameter in both or all modes of operation.

Abstract: A detector comprises a detector base (1) and first and second detector elements (2 & 3) each having a respective electronic interface (2a, 3a). The detector base (1) has electronic interfaces (1a) to the electronic interface (2a, 3a) of each of the detector elements (2, 3), wherein at least one of the detector elements is constructed as a replaceable module (11).

Abstract: A detector comprises a detector base and a sensor, first and second resistors connected in series, a DC voltage source (Vref) connected to the resistors, and means for monitoring the voltage at the midpoint of a potential divider constituted by the series-connected resistors. The first and second resistors are rated so that the midpoint voltage is indicative of the date of manufacture of the sensor.

Abstract: A detector comprises a housing (1), a pyroelectric array sensor (2) mounted within the housing, a heater (4) associated with the pyroelectric array sensor, and control means (6) for varying the power supplied to the heater to control the temperature of the pyroelectric array sensor relative to the ambient temperature in order to minimise the rate of change of temperature of the pyroelectric array sensor and to keep a predetermined difference between the temperature of the pyroelectric array sensor and the ambient temperature.

Abstract: A detection system in which a single sensor is employed to detect an extensive range of a parameter. The output signal from the sensor is fed to the input of the electrical circuit, having a feedback loop, wherein the electrical circuit has a non-linear transfer characteristic. The non-linear transfer characteristic is achieved by changing the behavior of the feedback loop of the electrical circuit at a predetermined level of input signal. The output of the circuit has a proportional relationship with the input until the input signal reaches this predetermined value, whereupon the behaviors of the feedback loop changes and the relationship of the output to the input of the circuit changes. While the input signal is above the predetermined value, the output of the circuit has a linear but disproportionate relationship with the input at a gradient different to that when the input signal is below the predetermined value.

Abstract: A method is disclosed for testing the functionality of a sensor (1) of a fire detector during operation thereof. The method comprises applying a current-limited test signal to the sensor (1), the test signal being such that the impedance of the sensor is such as to absorb the current-limited test signal when the sensor is operating normally; and applying the output of the sensor to a test signal detector (7). The arrangement is such that the test signal passes the output terminal of the sensor (1) only when the sensor is not operating normally.