GB2251684A - Method and apparatus for detecting fire - Google Patents
Method and apparatus for detecting fire Download PDFInfo
- Publication number
- GB2251684A GB2251684A GB9127281A GB9127281A GB2251684A GB 2251684 A GB2251684 A GB 2251684A GB 9127281 A GB9127281 A GB 9127281A GB 9127281 A GB9127281 A GB 9127281A GB 2251684 A GB2251684 A GB 2251684A
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- 238000000034 method Methods 0.000 title claims description 29
- 230000005855 radiation Effects 0.000 claims abstract description 16
- 238000012544 monitoring process Methods 0.000 claims abstract description 5
- 238000010606 normalization Methods 0.000 claims description 9
- 230000002596 correlated effect Effects 0.000 claims description 2
- 230000000694 effects Effects 0.000 claims 1
- 238000001514 detection method Methods 0.000 description 6
- 230000035945 sensitivity Effects 0.000 description 5
- 238000010586 diagram Methods 0.000 description 3
- 238000001228 spectrum Methods 0.000 description 3
- 238000012795 verification Methods 0.000 description 2
- 230000003321 amplification Effects 0.000 description 1
- 230000001276 controlling effect Effects 0.000 description 1
- 230000008878 coupling Effects 0.000 description 1
- 238000010168 coupling process Methods 0.000 description 1
- 238000005859 coupling reaction Methods 0.000 description 1
- 230000003247 decreasing effect Effects 0.000 description 1
- 230000003111 delayed effect Effects 0.000 description 1
- 229910052736 halogen Inorganic materials 0.000 description 1
- 150000002367 halogens Chemical class 0.000 description 1
- 229940052961 longrange Drugs 0.000 description 1
- 238000012986 modification Methods 0.000 description 1
- 230000004048 modification Effects 0.000 description 1
- 229910052754 neon Inorganic materials 0.000 description 1
- GKAOGPIIYCISHV-UHFFFAOYSA-N neon atom Chemical compound [Ne] GKAOGPIIYCISHV-UHFFFAOYSA-N 0.000 description 1
- 238000003199 nucleic acid amplification method Methods 0.000 description 1
- 230000000737 periodic effect Effects 0.000 description 1
- 238000005070 sampling Methods 0.000 description 1
- 238000012360 testing method Methods 0.000 description 1
- 230000036962 time dependent Effects 0.000 description 1
- 238000003466 welding Methods 0.000 description 1
Classifications
-
- G—PHYSICS
- G08—SIGNALLING
- G08B—SIGNALLING OR CALLING SYSTEMS; ORDER TELEGRAPHS; ALARM SYSTEMS
- G08B29/00—Checking or monitoring of signalling or alarm systems; Prevention or correction of operating errors, e.g. preventing unauthorised operation
- G08B29/18—Prevention or correction of operating errors
-
- G—PHYSICS
- G08—SIGNALLING
- G08B—SIGNALLING OR CALLING SYSTEMS; ORDER TELEGRAPHS; ALARM SYSTEMS
- G08B17/00—Fire alarms; Alarms responsive to explosion
- G08B17/12—Actuation by presence of radiation or particles, e.g. of infrared radiation or of ions
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- Physics & Mathematics (AREA)
- General Physics & Mathematics (AREA)
- Business, Economics & Management (AREA)
- Emergency Management (AREA)
- Engineering & Computer Science (AREA)
- Computer Security & Cryptography (AREA)
- Fire-Detection Mechanisms (AREA)
- Fire Alarms (AREA)
Abstract
A fire condition in a monitored space is detected by: storing in a memory 6 a reference signal representing the fire condition to be detected; continuously monitoring the monitored space by a sensor system 2 which generates monitored signals representing the radiation condition of the monitored space; and cross-correlating the monitored signals generated by the sensor system with the stored reference signals to produce a correlation coefficient indicating the degree of correlation between the two signals, and thereby the presence or absence of a fire condition in the monitored space. <IMAGE>
Description
2 2516 34 METHOD AND APPARATUS FOR DETECTING FIRE The present invention
relates to a method and also to apparatus for detecting a fire condition in a monitored space.
One of the problems in detecting fire conditions, particularly at long ranges, is the high false alarm rate. Thus, the range of detection can be increased by increasing the sensitivity of the system, e.g., by setting the amplification level and/or the threshold level. However, 10, this manner of increasing the sensitivity of a fire detection system also tends to increase the false alarm rate. This is because spurious radiation sources, such as matches, sunlight, and artificial light, which might not actuate short-range detectors, tend to activate detectors whose sensitivity has been increased - in order to increase the range. A false alarm may result in a costly discharge of the fire extinguisher; and if the fire extinguisher is of a type requiring replacement before reuse, the false alarm may disable the fire extinguisher system until it has been replaced.
A number of attempts have been made for increasing the range of a fire detector' system without substantially increasing the false alarm rate. Some described systems utilize two sensors in different spectrum ranges, as illustrated in US Patents-3,653,016, 3,665,440, 3,825,754 and 3,931,521. Other described systems an AC coupling and a level ratio test, as illustrated in US Patent 4,455,487. Insofar as we are aware, however, such described systems have not proved satisfactory for long- range fire detection with an acceptable low level of false alarm.
In another proposed system, the detector examines the frequency characteristics of monitored signals produced by a sensor, in order to distinguish between fire-produced radiation and spurious radiation. However, such a proposed system was also not found entirely satisfactory because the 1 spurious radiation source frequency has natural fluctuations in the same frequency band as the fire.
An object of the present invention is to provide a method, and also apparatus, for detecting a fire condition in a monitored space which is capable of long-range fire detection with a relatively low rate of false alarms.
According to the present invention, there is provided a method of detecting a fire condition in a monitored space, comprising the steps.: storing in a memory a reference signal representing the fire condition to be detected; continuously monitoring the monitored space by a sensor system which generates monitored signals representing the radiation condition of the monitored space; cross-correlating the monitored signals generated by the sensor system with the stored reference signals to produce a correlation coefficient indicating the degree of correlation between the two signals,4 comparing the correlation coefficient with a predetermined threshold value; and generating a positive output signal indicating the presence of a fire condition in the monitored space when the correlation coefficient is equal to or above the predetermined threshold, and a negative output signal indicating the absence of a fire condition in the monitored space when the correlation coefficient is below the predetermined threshold.
According to fiirther features in the preferred embodiment of the invention described below, the stored reference signal is normalized to a predetermined norm, and the monitored signals are also normalized to the same predetermined norm before being cross-correlated with the reference signal. Such a normalization thus enables detection in any range based on signal characteristics and not on signal levels. The reference signal and the monitored signals may be normalized statistically by autocorrelation.
According to further features in the preferred embodiment of the invention described below, the method includes the further steps of computing the energy in at least two frequency bands of the monitored signals; and generating a negative output signal indicating the absence of a fire condition in the monitored space if the energy in each of the at least two frequency bands is not above a predetermined value. Thus, in the case of a fire condition, the monitored signals will include energy in several frequency bands, whereas in the case of spurious periodic signals, there is a greater liklihood that one of the monitored bands will include no energy; in such case, the negative output signal is immediately generated to indicate the absence of a fire irrespective of the result of the cross-correlation operation, thereby decreasing the possibility of false alarms. The energy in the at least two frequency bands may be computed by the use of filters; alternatively,.it may be computed by performing a Fast Fourier Transform operation on the monitored signals. Preferably, the energy is computed in the 0.5-4 Hz and 5-8 Hz bands. 20 According to further features in the preferred embodiment of the invention described below, the sensor circuit senses infrared radiation, but may also include an ultraviolet sensor for sensing ultraviolet radiation. Thus, if the ultraviolet radiation sensed is below a predetermined level, the sensor is effective to generate a negative output signal indicating the absence of a fire condition irrespective of the cross- correlation operation, thereby further reducing the possibility of false alarms.
According to further features in the described preferred embodiment, the reference signal is stored in digital form, and the monitored signals are converted to digital form before being cross- correlated with the reference signal. A plurality of reference signals may be stored indicating different types of fire conditions, in which case the monitored signals would be cross-correlated with each of the stored reference signals to indicate not - 4 only the presence of a fire condition, but also the type in the monitored space.
According to further features in the described embodiment, the reference signal is produced by exposing the sensor system to a fire condition of the type to be detected, and storing the output of the sensor system.
A method in accordance with the above features is capable of detecting a fire condition in a monitored space at relatively long range and with a relatively low rate of false alarms.
The invention also provides an apparatus for detecting a fire condition in accordance with the above method.
Further features and advantages of the invention will be apparent from the description below.
The invention is herein described, by way of example only, with reference to the accompanying drawings, wherein:
Fig. 1 is a block diagram illustrating one form of apparatus constructed and operating in accordance with the present invention; 1 Fig. 2 is a flow chart illustrating the procedure for producing and storing the reference signal or signals to be used in the method of the present invention; and Fig. 3 is a flow chart illustrating the operation of 'the signal processor 'in the system of Fig. 1.
The apparatus illustrated by the block diagram of Fig. 1 comprises a sensor system including an infrared detector 2 and an ultraviolet detector 4 continuously monitoring a predetermined space to automatically indicate when a fire condition occurs. The illustrated apparatus further includes a storage device 6 for storing a reference signal representing the fire condition to be detected. The monitored signals from the infrared radiation detector 2 are fed via a filter 8 and an analog-to-digital converter 10 to a signal processor 12 which processes the digital signals in a manner to be described more particularly below with respect to the flow chart of Fig. 3.
One of the operations performed by signal processor 12 is to crosscorrelate the monitored signals from the infrared detector 2 with the reference signal stored in storage device 6 and to produce a correlation coefficient indicating the degree of correlation between the two signals. Signal processor 12 further compares the coefficient correlation with a predetermined threshold value. If the correlation coefficient is equal to or above the predetermined threshold value, signal processor 12 outputs a positive output signal indicating the presence of a fire condition in the monitored space. On the other hand, if the correlation coefficient is below the predetermined threshold, signal processor 12 outputs a negative output signal indicating the absence of a fire condition in the monitored space. The signal outputted by signal processor 12 is fed, via output interface circuitry 14, to actuate a fire alarm 16, and/or a fire extinguisher 18, if the output signal is positive indicating the presence of a fire condition.
The apparatus illustrated in the block diagram of Fig. 1 further includes a DC control circuit 20 controlling the infrared detector 2. The normalization of the signal outputted by the infrared detector 2 may be effected statistically in signal -processor 12. The reference signal stored in storage device 6 is also normalized to the same predetermined norm so that when the monitored signals from the detector 2 are cross-correlated with the reference signal in the signal processor 12, the correlation will be based on signal characteristics and will not be affected by signal levels.
The provision of the ultraviolet detector 4 in the sensor system is optional and is intended primarily to reduce the false alarm rate. Thus, if the output of the ultraviolet detector 4 is below a minimum value, this would indicate that the monitored signal is a spurious signal, 6 - e.g., from a vehicle headlight or the like and not from a fire condition. Accordingly, when the output of the ultraviolet detector 4 is below a minimum value, this is detected by a logic circuit 22 which is connected to the signal processor 12 and is effective to cause the signal processor to generate a negative output signal, indicating the absence of a fire condition, irrespective of the results of the cross-correlation of the monitored signals with the reference signal.
Fig. 2 is a flow chart illustrating the manner of producing and storing the reference signal in the reference signal storage device 6. This is done by exposing the sensor system, e.g., the infrared detector 2 in Fig. 1, to a fire condition of the type to be detected, thereby causing the sensor to output electrical signals representing the fire condition (block 30). The signals outputted by the infrared detector are then used for computing the energy in at least two frequency bands (block 32). 20 The reference signal is then stored in storage device 6 (block 36). After the reference signal has been generated and stored in the storage device 6 of Fig. 1, the system illustrated in Fig. 1 may be used for detecting a fire condition in the monitored space. This is done by continuously cross-correlating in the signal processor 12 the monitored signals outputted by the infrared detector 2 with the reference signal stored in storage device 6, to produce a correlation coefficient indicating the degree of correlation between the two signals. The operations performed in the signal processor 12-are indicated by the flow chart illustrated in Fig. 3.
Thus, the output of infrared detector 2 is sampled to produce a sequence of monitored signals (block 40). Such monitored signals are also analyzed for the energy content in at least two frequency bands (block 42), and are also normalized to the same predetermined norm as the reference 7 - signal (indicated by blocks 32 and 34 in Fig. 2). After the monitored signals have thus been processed to compute the energy in the two selected bands and normalized, each monitored signal is cross-correlated with the reference signal stored in the storage device 6.
As indicated earlier, the normalization of the monitored signals, as well as of the reference signal, is done statistically by auto-correlation. The auto-correlation process, as well as the cross-correlation process, is performed by moving one signal over the other and summing the product of all points, according to the following equation: Auto-Correlation:
R-AV, (,-() = Cross -Correlation:
P, vy C-() -- wherein:
1 ti - /'( __j- r', - ir ri 2----?1- c - -x- L 4 7' + N = number of samples; th xl = the input signal at the i sample; the delay time (the number of samples in the delayed signal); and Y1 the second input signal.
The result of the correlation is a time dependent signal. This signal is statistically normalized by the calculation of the power spectrum. The power spectrum is used as the normalization coefficient. The normalization will make the maximum level of an auto-correlation to equal exactly 1.0, and can be done on-line or off-line. -The process of normalization neutralizes the level of the signal, thus enabling detection in any range. based on signal characteristics, and not on signal level.
The normalization factor (NF) is determined as follows:
NF Z wherein:
Rxx(o) = auto-correlation of "x" at delay time of "0"; Ryy(O) = auto-correlation of "y" at delay time of "0"; N = number of samples.
Returning to the flow chart of Fig. 3, it will be seen that the normalized monitored signals (block 44) are cross-correlated (in block 46) with the stored normalized reference signal (block 48) to produce a correlation coefficient indicating the degree of correlation between the two signals; thus, a perfect correlation would produce a correlation coef f icient of " 1. 0". The correlation coefficient is compared (in block 50) with a predetermined threshold level (provided by block 52), and if it is not above the predetermined threshold level, a negative output signal is produced indicating the absence of a fire condition in the monitored space (block 54).
On the other hand, if the correlation coefficient is above the predetermined threshold level, a further check is made (in block 56) whether the ultraviolet detector (4, Fig. 1) produced an output above a predetermined level; and if not, a negative output signal is produced also indicating the absence of a fire condition in the monitored space (block 58).
If the ultraviolet detector output is above a predetermined level, thereby indicating the presence of a fire condition in the monitored space, a further check is made (block 60) as to whether further verification- is needed; if not, a positive signal is outputted by the signal processor (12, Fig. 1) indicating the presence of a fire condition, which output signal may actuate a fire alarm (16, Fig. 1), as shown by block 62 in Fig. 3, and/or a fire extinguisher (18, Fig. 1).
On the other hand, if further verification of the presence of a fire condition is needed in order to reduce 1 the false alarm rate, the system checks the energy in both the 0.5-4 Hz band (block 64), and in the 5-8 Hz band (block 66). If a predetermined minimum energy level is found to be present in both bands (block 68), thereby verifying that a fire condition exists, the positive output signal is produced from the signal processor 12 to activate the fire alarm (block 62), and/or the fire extinguisher (18, Fig. 1).
On the other hand, if the predetermined minimum level of energy is not found to be present in either one of the selected bands, a negative output signal is produced indicating the absence of a fire condition (block 70).
In order to further reduce the false alarm rate, the further verification (block 60) may also include the correlation of the monitored signal (block 72) with a false alarm signal threshold (from block 74), and if the resulting correlation coefficient is above the predetermined reference leve (block 76), a positive output signal is produced indicating the presence of a fire condition (block 62), whereas if it is below the reference level, a negative output signal is produced indicating the absence of a fire condition (block 70).
As one example, the system may be implemented by using a personal computer (PC), such as a 80386 PC. A data acquisition board, including an analog-to-digital converter, may be inserted into the PC. The operation of the board is effected by a software module, and the data sampled is accessible by software via a DOS operating system.
The software may be written in Pascal language. The monitored signal may be sampled 480 times per second until 2,000 points are sampled. The reference signal containing 2,000 points may be saved on a hard disc. After the sampling of the monitored signal has been completed, the reference file and the sampled data file are opened, and the system performs the above-described cross-correlation process. The correlation may be done on every fifth point, and only on the 1,000 middle points to save computation time.
- If a check is also made, as described above, of the relative energy in two selected frequency bands, the two frequency bands may be the 0.5-4 Hz band and the 5-8 Hz band. This may be done by a Fast Fourier Transform operation. The fire alarm signal may be activated only when it is found that the energy level in both bands is at least 0.06 (6%) of the total energy.
If both an infrared sensor (2, Fig. 1) and an ultraviolet sensor (4, Fig. 1) are used, the infrared sensor may have largest sensitivity in the range of 1.5 to 3 lim, and the UV sensor may have largest sensitivity in the range of 200 nm. As indicated above, the UV sensor may be used as a go-nogo indicator, such that if the minimum level of UV is not found to be present, the cross-correlation process is not performed.
A system constructed in accordance with the foregoing was tested and found to be able to detect a standard fire of 1 foot x 1 foot at a distance of 50 metres. The system was tested using several spurious radiation sources, including direct and reflected sunlight, arc welding, neon lamps, vehicle headlights, halogen lamps, and no false alarm was observed.
While the invention has been described with respect to one preferred embodiment, it will be appreciated that many variations, modifications and other applications of the invention may be made.
Claims (28)
1. A method of detecting a fire condition in a monitored space, comprising the steps:
storing in a memory a reference signal representing the fire condition to be detected; continuously monitoring the monitored space by a sensor system which generates monitored signals representing the radiation condition of the monitored space; cross-correlating the monitored signals generated by the sensor system with said stored reference signals to produce a correlation coefficient indicating the degree of correlation between the two signals; comparing the correlation coefficient with a predetermined threshold value, and generating a positive output signal indicating the presence of a fire condition in said monitored space when the correlation coefficient is equal to or above said predetermined threshold, and a negative output signal indicating the absence of a fire condition in said monitored space when the correlation coefficient is below said predetermined threshold.
2. The method according to Claim 1, wherein said stored reference signal is normalized to a predetermined norm, and said monitored signals are also normalized to the same predetermined norm before being cross- correlated with the reference signal.
3. The method according to Claim 2, wherein the normalization of the reference signal and the monitored signals is effected statistically by auto-correlation.
4. The method according to any one of Claims 1-3, including the further steps of:
computing the energy in at least two frequency bands of the monitored signals; and generating a negative output signal indicating the absence of a fire condition in the monitored space if the energy in each of said at least two frequency bands is not above a predetermined value.
1 12 -
5. The method according to Claim 4, wherein the energy in said at least two frequency bands is computed by the use of filters.
6. The method according to Claim 4, wherein the energy in said at least two frequency bands is computed by performing a Fast Fourier Transform operation on said monitored signals.
7. The method according to any one of Claims 4-6, wherein the energy in the monitored signals is computed in the 0.5-4 Hz and 5-8 Hz bands.
8. The method according to any one of Claims 1-7, wherein said sensor system senses infrared radiation.
9. The method according to any one of Claims 1-8, wherein said sensor system also senses ultraviolet radiation and is effective to generate a negative output signal indicating the absence of a fire condition in the monitored space if the sensed ultraviolet radiation is below a predetermined value.
10. The method according to any one of Claims 1-9, wherein said reference signal is storea in digital form, and said monitored signals are converted to digital form before being cross-correlated with said reference signal.
11. The method according to any one of Claims 1-10, wherein said reference signal is stored by exposing said sensor system to a fire condition of the type to be detected and storing the output of said sensor system.
12. The method according to any one of Claims 1-11, wherein a plurality of reference signals are stored indicating different types of fire conditions, and said monitored signals are cross-correlated with each of said stored reference signals to indicate.the presence and type of a fire condition in the monitored space.
13. Apparatus for detecting a fire condition in a monitored space, comprising:
storage means for storing a reference signal representing the fire condition to be detected; a sensor system for continuously monitoring the monitored space and for generating monitored signals representing the condition of the monitored space; cross-correlation means for cross-correlating the monitored signals generated by the sensor system with the stored reference signals to produce a correlation coefficient indicating the degree of correlation between the two signals; comparing means for comparing the correlation coefficient with a predetermined threshold value; and generating means for generating a positive output signal indicating the presence of a fire condition in the monitored space when the correlation coefficient is equal to or above said predetermined threshold, and for generating a negative output signal indicating the absence of a fire condition in the monitored space when the correlation coefficient is below said predetermined threshold.
14. The apparatus according to Claim 13, wherein said sensor system outputs an analog signal, and said apparatus includes an analog-todigital converter for converting said analog signal to digital form, and wherein said cross-correlation means, comparing means and generating means, are all included in a digital data processor.
15. The apparatus according to Claim 14, further including normalizing means for normalizing the stored reference signal to a predetermined norm, and for normalizing said monitored signals to said predetermined norm before they are cross-correlated with the reference signal.
16. The apparatus according to Claim 15, wherein said normalizating means is included in said digital data processor which effects the normalization of the reference signal and of the monitored signals statistically by auto-correlation.
17. The apparatus according to any one of Claims 14-16, further including means for computing the energy in at least two frequency bands of the monitor signals and for generating a negative output signal indicating the absence of a fire condition in the monitored space if the energy in each of said at least two frequency bands is not over a predetermined value.
18. The apparatus according to Claim 17, wherein said latter means includes filters for said at least two frequency bands.
19. The appaaratus according to Claim 17, wherein said latter means is included in the data processor which performs a Fast Fourier Transform operation on the monitored signals.
20. The apparatus according to any one of Claims 17-19, wherein said energy computer means computes the energy in the 0.5-4 Hz band and 5-8 Hz band.
21. The apparatus according to any one of Claims 13-20, wherein said sensor system includes an infrared sensor.
22. The apparatus according to any one of Claims 13-21, wherein said sensor system includes an ultraviolet sensor and is effective to generate a negative output signal indicating the absence of a fire condition in the monitored space if the sensed ultraviolet radiation is not above a predetermined value.
-
23. The apparatus according to any one of Claims 13 22, wherein said sensor system includes a TV camera and an image processor which computes the difference between frames to generate said monitored signals.
24. The apparatus according to any one of Claims 1323, wherein said storage means stores a plurality of reference signals indicating different types of fire conditions, and said cross-correlation means cross-correlates said monitor siganls with each of said stored reference signals to indicate the presence and type of fire condition, if any, in the monitored space.
25. The apparatus according to any one of Claims 13-24, further including a fire alarm which is actuated when 1, a positive output means.
26. The apparatus according to any one of Claims 13-25, further including a fire extinguisher which is actuated when a positive output signal is generated by said generating means.
27. The method of detecting a fire condition in a predetermined space substantially as described with reference to and as illustrated in the accompanying drawings.
28. Apparatus for detecting a fire condition in a monitored space, substantially as described with reference to and as illustrated in the accompanying drawings.
signal is generated by said generating
Applications Claiming Priority (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| IL96800A IL96800A0 (en) | 1990-12-27 | 1990-12-27 | Method and apparatus for detecting fire |
Publications (2)
| Publication Number | Publication Date |
|---|---|
| GB9127281D0 GB9127281D0 (en) | 1992-02-19 |
| GB2251684A true GB2251684A (en) | 1992-07-15 |
Family
ID=11061893
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| GB9127281A Withdrawn GB2251684A (en) | 1990-12-27 | 1991-12-23 | Method and apparatus for detecting fire |
Country Status (3)
| Country | Link |
|---|---|
| DE (1) | DE4142419A1 (en) |
| GB (1) | GB2251684A (en) |
| IL (1) | IL96800A0 (en) |
Cited By (1)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| US6788208B2 (en) | 2002-02-04 | 2004-09-07 | Minimax Gmbh | Method for controlling stationary fire-extinguishing systems |
Families Citing this family (5)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| DE4242936A1 (en) * | 1992-12-18 | 1994-06-23 | Beckhausen Karlheinz | Safety device with microprocessor |
| DE4327229A1 (en) * | 1993-08-13 | 1995-02-16 | Abb Patent Gmbh | Device for setting at least one manipulated variable related to a specific manipulated variable in a motion detector |
| ES2160840T3 (en) * | 1995-09-16 | 2001-11-16 | Cit Alcatel | METHOD AND APPLIANCE FOR DETECTING AND EVALUATING SIGNAL DESIGNS ATTRIBUTABLE TO PARTICULAR PHYSICAL PROCESSES. |
| DE19741783A1 (en) * | 1997-09-22 | 1999-04-01 | Siemens Ag | Movement detection method for alarm system |
| GB2366369B (en) * | 2000-04-04 | 2002-07-24 | Infrared Integrated Syst Ltd | Detection of thermally induced turbulence in fluids |
Citations (1)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| WO1986006859A2 (en) * | 1985-05-17 | 1986-11-20 | Santa Barbara Research Center | Fire sensor cross-correlator circuit and method |
-
1990
- 1990-12-27 IL IL96800A patent/IL96800A0/en unknown
-
1991
- 1991-12-20 DE DE4142419A patent/DE4142419A1/en not_active Withdrawn
- 1991-12-23 GB GB9127281A patent/GB2251684A/en not_active Withdrawn
Patent Citations (1)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| WO1986006859A2 (en) * | 1985-05-17 | 1986-11-20 | Santa Barbara Research Center | Fire sensor cross-correlator circuit and method |
Cited By (1)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| US6788208B2 (en) | 2002-02-04 | 2004-09-07 | Minimax Gmbh | Method for controlling stationary fire-extinguishing systems |
Also Published As
| Publication number | Publication date |
|---|---|
| GB9127281D0 (en) | 1992-02-19 |
| DE4142419A1 (en) | 1992-07-02 |
| IL96800A0 (en) | 1991-09-16 |
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| WAP | Application withdrawn, taken to be withdrawn or refused ** after publication under section 16(1) |