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 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 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 comprising a 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 comprises 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 of the range of identification numbers, wherein upon completion of a scan that does not give rise to invalid responses, the previously-paused scan is resumed.

Abstract: A method of monitoring an alarm system comprises transmitting a sound alert signal, receiving the transmitted sound alert signal, comparing the received sound alert signal with a reference signal having parameters dependent upon equivalent parameters of the transmitted sound alert signal, and outputting a signal indicating whether or not the equivalent parameters of the received sound alert signal have a predetermined relationship with said parameters of the transmitted sound alert signal.

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 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 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 behaviour 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 behaviour 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 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.