Manual call point

Abstract

A manual call point for a fire alarm system, the manual call point includes: an operating element 18, wherein a physical movement of the operating element 18 will trigger an alarm condition of the manual call point; at least two switch devices 12, 14, 16. Each switch device 12, 14, 16 is arranged to complete or break a circuit in response to the physical movement of the operating element 18. At least one of the switch devices 12, 14, 16 is a contactless device 12, 14 and the corresponding circuit includes an electromagnetic circuit that is completed or broken without mechanical contact from the operating element 18.

Claims

1. A method of use of a manual call point for a fire alarm system, the manual call point comprising: an operating element, wherein a physical movement of the operating element will trigger an alarm condition of the manual call point; and at least two switch devices, with each switch device being for completing or breaking a circuit in response to the physical movement of the operating element; wherein at least one of the switch devices is a contactless switch and the corresponding circuit includes an electromagnetic circuit that is completed or broken without mechanical contact from the operating element wherein the contactless switch is provided by electromagnetic circuits comprising a light emitting diode paired with a photodiode; the method comprising at least one of: operating the manual call point by triggering the alarm condition by physical movement of the operating element to change the state of at least one of the switch devices; and self-verification by the manual call point; wherein the self-verification includes steps to confirm that at least one of the switch devices is operational without activation of the operating element; wherein the at least two switch devices include the contactless switch and a further contactless switch; and wherein the self-verification includes steps for cross-checking the operation of the two contactless switches, by using a receiver component of one switch to check the operation of an emitter component of the other switch.

2. A manual call point for a fire alarm system, the manual call point comprising: an operating element, wherein a physical movement of the operating element will trigger an alarm condition of the manual call point; and at least two switch devices, with each switch device being for completing or breaking a circuit in response to the physical movement of the operating element; wherein at least one of the switch devices is a contactless switch and the corresponding circuit includes an electromagnetic circuit that is completed or broken without mechanical contact from the operating element; wherein the at least two switch devices include the contactless switch and a further contactless switch, wherein the two contactless switches include a contactless optical switch that is arranged to be normally closed and a contactless optical switch that is arranged to be normally open; wherein an emitter component of one contactless optical switch is placed on a first side of the operating element alongside a receiver component of the other contactless optical switch, with the receiver component of the one contactless optical switch being placed on a second side of the operating element alongside an emitter component of the other contactless optical switch; and wherein the call point or an associated external controller is arranged to assess the interaction between components of the two contactless optical switches as a part of a self-verification procedure, and wherein the self-verification includes steps for cross-checking the operation of the two contactless optical switches, by using a receiver component of one contactless optical switch to check the operation of an emitter component of the other contactless optical switch.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

(1) Certain preferred embodiments of the present invention will now be described, by way of example only, with reference to the following drawings, in which:

(2) FIG. 1 is a diagram of a manual call point in a normal condition;

(3) FIG. 2 is a diagram of the manual call point after activation of an operating element to trigger an alarm condition; and

(4) FIG. 3 is a plot of an output signal for an example contactless switch.

DETAILED DESCRIPTION

(5) As shown in the Figures a manual call point includes a body 10 housing switches 12, 14, 16 and an operating element 18. The switches 12, 14, 16 include two contactless switches 12, 14 and an electromechanical switch 16. The electromechanical switch 16 can include a micro switch, for example. The contactless switches 12, 14 are advantageously similar or identical switches, using the same operating principle and similar components. This reduces the number of differing parts required as well as enhancing the ability of the call point to perform a self-verification process as discussed further below. The operating element 18 is a mechanical component that physically moves when the manual call point is activated and enters an alarm condition. FIG. 1 shows the operating element 18 with the manual call point in the normal condition, i.e. with no alarm. FIG. 2 shows the state after activation of the manual call point by movement of the operating element 18, which in this case will change the state of the electromechanical switch 16 by mechanical contact, as well as changing the state of the two contactless switches 12, 14 due to a change in the influence of the operating element 18 on those switches 12, 14.

(6) The contactless switches 12, 14 may be implemented in various ways such as with differing types of electromagnetic switches as discussed above. The influence of the operating element 18 on the contactless switches 12, 14 can hence vary accordingly, e.g. via influence on the relevant electromagnetic circuit. In this example the contactless switches 12, 14 are optical switches using light emitting diodes (LEDs) and light sensors in the form of photodiodes. The first contactless switch 12 includes an optical circuit with a first LED 20 and a first photodiode 22. The second contactless switch 14 includes an optical circuit with a second LED 26 and a second photodiode 24.

(7) As shown, the first contactless switch 12 is normally open, i.e. it is open in the normal condition of the manual call point with the operating element 18 in the position shown in FIG. 1, whereas the second contactless switch 14 is normally closed. Thus, in the normal condition of FIG. 1 light can pass from the second LED 26 with a direct line of sight 28 to the second photodiode 24, whereas the operating element 18, which is opaque to the relevant wavelengths, blocks the passage of light from the first LED 20 to the first photodiode 22. If the operating element 18 is activated, which in this example involves moving from the position of FIG. 1 to that of FIG. 2, then along with the mechanical contact that changes the state of the electromechanical switch 16, there is also a change in the influence of the operating element 18 since the line of sight for light from the second LED 26 to the second photodiode 24 is blocked, whereas a line of sight 30 from the first LED 20 to the first photodiode 22 is opened. The normally closed switch becomes open and the normally open switch becomes closed.

(8) The activation of the alarm condition can rely on any one switch changing state, thereby increasing reliability by providing redundancy in the event of a failure of a switch. Also, if an activation of the alarm condition is triggered with fewer than all three switches changing state then this can be used as an alert indicating a possible failure, so that the manual call point can be inspected and, if needed, repaired or replaced.

(9) The operating element 18 is some mechanical device activated by user interaction, such as a sliding or hinged actuating piece. The manual call point may also include a frangible element (not shown) such as a frangible element of the type described in EN 54-11. In that case the operating element 18 can be directly operated via breakage or displacement of the frangible element, or indirectly operated by user interaction once breakage or displacement of the frangible element gives access to the operating element 18. Other features of the manual call point, such as the size and form of the housing 10 may be provided in accordance with applicable regulatory requirements, such as regulations in line with EN 54-11. The manual call point may be configured for wired and/or wireless connectivity, such as to be connected with an alarm system of a building.

(10) The manual call point can perform a self-verification procedure in order to determine if at least one of the contactless switches 12, 14 is functional without the need to activate the operating element 18. This gives an advantage over traditional electromechanical devices where physically movement of the operating element 18 is necessary to test the device, and hence a person must be physically present. With the ability to perform self-verification it becomes possible to remotely check at least some aspects of the device function, e.g. checking the contactless switches 12, 14 even if the electromagnetic switch 16 can only be tested with physical presence and movement of the operating element 18. The self-verification procedure may be performed via controller, such as a microprocessor, which may be a controller provided as a part of the manual call point or an external controller, which may for example be an alarm system of a building.

(11) To aid and enhance the self-verification capability the receiver and emitter components of the two contactless switches 12, 14 are placed either side of a working path for the operating element with the respective emitter components (LEDs 20, 26 in this example) and receiver components (photodiodes 22, 24 in this example) being diagonally apart from one another. The working path comprises the locations occupied by the operating element 18 during the normal condition or the alarm condition. The operating element 18 hence block or permit the passage of electromagnetic radiation between the receiver and emitter components in order to change the state of the contactless switches 12, 14. As seen in the Figures, the LED 20 of the first contactless switch 12 is placed on a first side of the operating element 18 alongside the photodiode 24 of the second contactless switch 14, with the photodiode 22 of the first contactless switch 12 being placed on a second side of the operating element 18 alongside the LED 26 the second contactless switch 14.

(12) The self-verification procedures include cross-checking the operation of the contactless switches 12, 14 via interaction between the LEDs 20, 26 and photodiodes 22, 24. The condition of the first LED 20 of the normally open first contactless switch 12 is checked by using the photodiode 24 of the second contactless switch 14 to detect light from the first LED 20. This can be aided by switching off the second LED 26, or by the use of LEDs with different wavelengths. The condition of the first photodiode 22 of the normally open first contactless switch 12 is checked by detecting light from the second LED 26. These steps also check the condition of the second LED 26 and second photodiode 24, with a further check being possible by straightforward confirmation that this second, normally closed, contactless switch 14 is indeed a closed switch, with the second photodiode 24 detecting light from the second LED 26 when it is illuminated, but not when it is not illuminated. It will be understood that the steps required for these self-verification procedures can be carried out automatically, without the need for any human intervention, including under the control of some remote system.

(13) In some implementations, the emitter components such as the LEDs 20, 26 may emit pulses rather than being constantly illuminated. With the use of constant illumination or with pulses the manual call point may include a suitable circuit, optionally with a microprocessor as noted above, for controlling the illumination of the emitter components and for providing appropriate signals based on the output of the receiver components. For example, with LEDs 20, 26 and photodiodes 22, 24 as in the Figures, the light collected by the photodiodes 22, 24 is electrically converted into a detection signal, which can be fed into an amplifier circuit that generates an amplified analog output signal. The analog amplified output signal can be converted to an output digital signal with an analog-to-digital converter and communicated to an evaluation module. In some examples, the evaluation module is part of the controller discussed above. The evaluation module can be provided with software that includes comparison algorithms for verifying the optical and electrical integrity of the call point by comparing the electric output of the switches with a predefined and verified output. This verification is based on software analysis in the controller.

(14) Referring now to FIG. 3, a time response plot is illustrated with the output digital signal from a photodiode shown as a function of time. The output digital signal is ultimately a function of the light received at the photodiode, which in this case is a light pulse such as from the respective LED. A nominal background signal is represented by A on the plot. In a simple case, for example with reference to FIG. 1 and considering the background signal for the normally closed contactless switch 14 the nominal background signal is present when the LEDs 20, 26 are inactive (e.g., off) then the plot for the output signal of the second photodiode 24 may vary as follows. When the second LED 26 becomes active (e.g., turned on), the output digital signal will increase to reach a maximum signal value that is represented by B on the plot. When the second LED 26 is switched off, the signal value will undershoot below the nominal signal A to a minimum signal value that is represented by C on the plot before it settles up to the nominal background signal A again. Alternatively, the nominal background signal may be present with the LED 26 active (e.g., on), and hence the level A may be somewhat higher than shown in FIG. 3. When the LED 26 then becomes inactive (e.g., off), the output digital signal will adjust to reach the minimum signal value C. When the LED is switched back on, the signal value will adjust to the maximum signal value B and overshoot the background level before it settles down to the nominal background signal A again. Therefore, it is the extreme values that are of significance, not necessarily the order in which the data is taken.

(15) It will be appreciated that with the arrangement of LEDs 20, 26 and photodiodes 22, 24 in the current example then as noted above the LED of the one contactless switch can have a secondary effect on the light received at the photodiode of the other contactless switch. Thus, there could be further plots of similar shape but lower extremes where, for example, the first LED 20 can lead to changes in the signal level from the second photodiode 24. Moreover, yet further plots would exist taking account of a background level with both LEDs 20, 26 active, and then just one or both LEDs 20, 26 changing state. The various possible plots each have measured signals A, B, C with expected values and this can be used to determine acceptable operational ranges within which a self-verification procedure will confirm that the two contactless switches 12, 14 are working correctly. The acceptable operational ranges can be based on theoretically determined values which are then experimentally refined.

(16) In an example implementation, the signal is plotted with voltage values and the nominal voltage VA should be between allowed values Vnom_min and Vnom_max. This verifies the offset voltage for the amplifier, that there is no ambient light leaking into the chamber, and that the amplifier is functioning properly. VA may drift for multiple possible reasons. For example, natural temperature effects may impact the signal and are acceptable within a limit. Light leakage detrimentally impacts the overall operation of the manual call point (when using optical sensing) and is not deemed acceptable. Amplifier and/or sensor failure is also not deemed acceptable.

(17) The comparison made by the evaluation module can focus on a ratio of differences of the measured signals. In particular, the following ratio is calculated: (VB−VA)/(VA−VC). This ratio is constant within a tolerance. This measure verifies the filter components in the amplifier circuitry. The measure is valid as long as the output is within amplifier saturation limits.

(18) There are alternative methods of determining the validity of the received light/signals. For example, a burst of analog to digital conversions can be made throughout the pulse, with the sum, or sum of squares, of the samples being calculated to determine the magnitude of the received signal. Additionally, the expected pulse can be stored in the memory of the controller. The measured pulse is then multiplied with a factor that is the ratio between the magnitude of the stored and measured pulse. After this multiplication (normalization), the measured waveform, and the difference must be below a predefined limit. In addition to one or more of the features described above, or as an alternative, the cross-correlation between the stored and measured pulse must be above a certain limit.

(19) Advantageously, comparing the ratio of differences provides detection light source/sensor failure, detection of amplifier failure or erroneous components in the amplifier circuitry. All detection and verification is done with software, thereby allowing for local or remote control of the process.

(20) It will be understood that some features described herein, such as a frangible element, are required by regulation such as with reference to EN54-11, and of course all such features for must be included for devices intended to be approved under those regulations. However, it should be appreciated that it is not essential to the function of the call point described herein, and in particular the function of the operating element and switches, for all such features to be present. Moreover, whilst all features defined in the relevant regulations are in effect essential for a commercial product, this is not the same as what is essential for implementing the present claims. Instead the claims themselves define what is essential in that regard, taking account of the teaching of the remainder of this disclosure.