baber/WOPTO huggingface dataset:
Patent GB-1529362-A (GB)
Title: Process for priming and compositions therefor
IPC: C09J183/00
Filed: 1975-10-08
Abstract: 1529362 Organo-silicon containing coating compositions DOW CORNING CORP 8 Oct 1975 [15 Oct 1974] 41203/75 Headings C3T and C3B [Also in Division B2] A film-forming composition comprises a homogeneous solution of (A) from 0À99 to 15% wt. of a compound selected from (1) compounds of the formula (RO) 4-a SiZ a , (2) curable reaction products of (a) silanes of the formula and (b) epoxy compounds soluble in (C) + (D) + (E) below and (3) siloxanes which are condensation and co-condensation products of (1) and (2), (B) from 0À01 to 10% wt., of at least one primer-soluble, light-fugitive colourant which will retain at least some of its colour for at least 24 hours and will subsequently become colourless, i.e. within a time period from 1 day to 6 weeks, in the presence of light, (C) from 1- 85% wt. of a solvent of the formula (D) from 1-85% wt. of a hydrocarbon solvent with a boiling point from 50‹ to 250‹ C., and (E) from 1-85% wt. of a solvent of the formula CH 3 CO(OCH 2 CH(Q)) y OR<SP>111</SP>, where a is 0 to 1, n is 3-9, y is 0-2, Q is hydrogen or methyl, R is an alkyl, cycloalkyl or alkoxyalkyl group containing less than 7 carbon atoms, R<SP>1</SP> is hydrogen or a -C m H 2m NH 2  group where m is 2-4, R<SP>111</SP> is an aliphatic or cycloaliphatic hydrocarbon radical containing not more than 9 carbon atoms, and Z is an alkyl, vinyl, phenyl or -C n H 2n NHR<SP>1</SP> group, any nitrogen atom being bonded to Si atoms through at least 3 carbon atoms, the percentages being based on the total weight of the composition. Suitable colourants are amaranth, brilliant blue, anthraquinone violet B, cyanine green, erythrosine, fluorescein, indigo carmine, metanil, yellow, sunset yellow, tartrazine, Violamine R, Congo red, primulin, auramine and safranin Y. Suitable solvents (C) are methanol, butanol, isopropanol, cyclohexanol, monoalkyl ethers of ethylene glycol, propylene glycol, diethylene glycol and dipropylene glycol. Suitable solvents (D) are benzene, toluene, xylene, cyclohexane, cyclohexene, heptane and petroleum naphtha. Suitable solvent (E) is ethoxyethylacetate. The compositions are used as primers on surfaces which are to be coated with silicone containing coating compositions, e.g. metals, such as Al, Fe, Cu and their alloys; wood; cementitious materials; marble, ceramics and glass; painted surfaces and porous plastics such as polyurethane foam and nylon cloth. In the examples a primer composition is prepared by dissolving a solid epoxy resin in a mixture of 2-methoxyethanol, toluene and 2- ethoxyethyl acetate, then adding aminoethylaminopropyl - trimethoxysilane and then an aqueous solution of tartrazine, brilliant blue and sunset yellow. The primer is either applied to concrete, marble and plywood surfaces and dried in air, or applied to a polyurethane foam surface, dried after which the primed foam is coated with a RTV organo-silicon containing coating composition.
Patent GB-1510795-A (GB)
Title: 2-(2'-chloro-3'-substituted-4-oxo)azetidinyl-3-methyl-3-butenoates
IPC: A61K31/535
Filed: 1975-06-30
Abstract: 1510795 2(2 - Chloro - 4 - oxo)azetidinyl- 3-methyl-3-butenoates QUEEN'S UNIVERSITY AT KINGSTON 30 June 1975 [6 Aug 1974] 41215/77 Divided out of 1510794 Heading C2C Novel 2 - (2 - chloro - 4 - oxo)azetidinyl- 3-methyl-3-butenoates of general formula wherein R<SP>8</SP> is H or RCO- or R<SP>8</SP>NH- forms a phthalimido group; R is C 1-5  alkyl, Ar-X-C(R<SP>5</SP>)(R<SP>6</SP>)-, Z<SP>1</SP>Z<SP>2</SP>Z<SP>3</SP>C- or R<SP>12</SP>-O-, Ar is a radical in which R, R 2  and R 3 , same or different, are H, Cl, Br, I, CF 3 , phenyl, C 1-5  alkyl or C 1-5  alkoxy, but only one may be phenyl; R<SP>4</SP> is H, -NH 2 , C 6 H 5 OCONH-, phenyl, F, Cl, Br, I, -COOH, -SO 3 H,-N 3 , -OH C 1-5  alkanoyloxy or C 1-5  alkoxy; X is -O- or -S-; R<SP>5</SP> and R<SP>6</SP> are each H, phenyl, benzyl, phenethyl or C 1-5  alkyl; Z<SP>1</SP>, Z<SP>2</SP> and Z<SP>3</SP> are each C 1-5  alkyl or on Ar group; R<SP>12</SP> is CCl 3 CH 2 - or benzyl; R<SP>1</SP> is H, alkyl, benzyl, benzhydryl, alkoxyalkyl, alkoxybenzyl, phenacyl, (CH 3 ) 3 Si-, CClCH 3  or pivaloyl groups, are prepared by debromination of a compound with 2-4 molar equivalents of Zn in an alkanoio acid. Alternatively a mixture of the 4-bromo- 3-methyl- and 3-bromomethylazetidinyl-but- 2-enoic acid derivatives may be debrominated with Zn in glacial acetic acid. The compounds 2-(2<SP>1</SP>R or 2<SP>2</SP>S-chloro-3<SP>1</SP>5-phthalimido-4<SP>1</SP>-oxo)- azetidinyl - 3 - methyl - 3 - butenoate and methyl or benzhydryl 2-(2<SP>1</SP>R-chloro-3<SP>1</SP>S-trichloroethoxycarbonylamino - 4<SP>1</SP>- oxo) azetidinyl-3-methyl-3-butenoate are described. 3-Methyl or 3-hydroxy-1-oxacephems of general formula are obtained from the compounds of the invention. Reference has been directed by the Comptroller to Specification 1,346,744.
Patent GB-1135369-A (GB)
Title: Adenosine acetals
IPC: C07H19/16
Filed: 1967-09-11
Abstract: 1,135,369. Adenosine acetals. C. F. BOEHRINGER & SOEHNE G.m.b.H. 11 Sept., 1967 [14 Sept., 1966], No. 41337/67. Heading C2C. Exo- and endo-compounds of the general formula (wherein R 1  is a halogen atom or lower alkyl radical and R 2  and R 3 , which may be the same or different, are hydrogen or halogen atoms or lower alkyl radicals) are prepared by reacting adenosine, in the presence of an acidic catalyst, with a compound of the formula or an acetal (which may be formed in situ) thereof. The lower alkyl radicals contain up to 3 carbon atoms. The compounds of the invention are characterized by good cardiac and circulatory effectiveness.
Patent GB-1072788-A (GB)
Title: Improvements in or relating to hydraulically driven screw presses
IPC: B30B1/23
Filed: 1964-10-12
Abstract: 1,072,788. Screw presses. MASCHINENFABRIK HASENCLEVER A.G. Oct. 12, 1964 [Nov. 8, 1963], No. 41474/64. Heading B5F. In a screw press having an hydraulic motor 4 for driving a screw 3 connected to a slide 2 (by tie members 2a), the motor 4 is controlled by reversing switches 7a, 7b operated shortly before the slide reaches the upper and lower ends of its stroke. Cylinder and piston units 10, 11 connected directly to the hydraulic motor supply act as brakes on the slide, and then initially aid the screw to reverse the motion of the slide to urge the tools 8, 9 together. The drive motor 4 is connected to an hydraulic accumulator (13) and drives the screw 3 through gearing 5, 6. The gear 6 may be constructed as a flywheel and the motor may be mounted in the base of the press.
Patent GB-1111495-A (GB)
Title: Linear silicon and/or germanium-containing polyamides,and processes for their preparation and application
IPC: C08G69/26
Filed: 1965-10-01
Abstract: Linear polyamides contain the repeating units <FORM:1111495/C3/1> wherein n and n1 are each integers greater than 3, R and R1 are each saturated or unsaturated branched or unbranched organic groups and M and M1 are each Si or Ge, and wherein some but not all of the groups -CH2-(CH2)n-MR2 -(CH2)n-CH2- and -(CH2)n1-M1R12-(CH2)n1\t - may be replaced by groups -(CH2)n11- and -(CH2)n111- respectively, where n11 and n111 are each an integer greater than 1.  They are prepared by heating an equimolecular mixture of R12M1[(CH2)n1COOH]2 or R2M[(CH2)nCH2NH2]2 with, respectively, an amine R2M[(CH2)nCH2NH2]2 or H2N(CH2)n11NH2 or an acid R12M1[(CH2)n1COOH]2 or HOOC(CH2)n111COOH for 2-3 hours at 150-250 DEG  C. in a closed vessel under an inert atmosphere, optionally in the presence of a catalyst.  The silicon-containing diacids and diamines above are prepared by hydrolysis and reduction, respectively, from the corresponding dinitriles, which are in turn prepared, via the dihalides, from the dialcohols; these are obtained from the diorganosilicon dihalide and a pyranyl-oxyalkyl magnesium halide, from the reaction product of which the pyranyl group is removed by hydrolysis.  In examples the preparation is described of polymers having the repeating units <FORM:1111495/C3/2> and <FORM:1111495/C3/3> and of the corresponding diacids and diamines.ALSO:Germanium-containing dicarboxylic acids and diamines are prepared by hydrolysis and reduction, respectively, of the corresponding dinitriles R2Ge[(CH2)nCN]2, where each R represents a saturated or unsaturated branched or unbranched organic group and n is an integer greater than 3.  The dinitriles are prepared, via the dihalides, from the dialcohols, which are obtained by hydrolytically removing the pyranyl group from the product of reaction of a diorganogermanium dihalide with a pyranyloxyalkyl magnesium halide. In Example 1 <FORM:1111495/C2/1> <FORM:1111495/C2/2> <FORM:1111495/C2/3> <FORM:1111495/C2/4> <FORM:1111495/C2/5> <FORM:1111495/C2/6>
Patent GB-1154417-A (GB)
Title: Improvements in or relating to Nuclear Fuel Elements
IPC: G21C3/18
Filed: 1967-09-13
Abstract: 1,154,417. Fuel elements. GULF GENERAL ATOMIC Inc. 13 Sept., 1967 [14 April, 1967], No. 41782/67. Heading G6C. A fuel element comprises nuclear fuel particles disposed in a fuel chamber with activated carbon having a surface area of at least 300 sq. m/gm. dispersed between the fuel particles. Such activated carbon acts to adsorb heavy ion fission products (e.g. Ba, Cs, Ce and Sr) and minimize their migration and release into the coolant circuit. A fuel element suitable for use in a high-temperature gas-cooled reactor, as shown in Fig. 2, comprises an elongated graphite body section 13 having a central bore 15 housing a moderator 28, e.g. BeO or BeC, and a plurality of cylindrical fuel chambers 17 which contain beds of particulate nuclear fuel material 19. The fuel particles may be of ThC 2  and enriched UC (in a 10: 1 ratio Th: U) and have a pyrolytic carbon coating. After being loaded into the fuel chambers 17, they are packed to maximum concentration by vibratory compaction. The body section 13 is disposed between top and bottom graphite reflectors 21, 23. The fuel element is supported by means of an upstanding pin engaging in a well 24 in the bottom reflector 23. A spacer ring 31 intermediate the ends of the top reflector 21 serves to laterally abut spacer rings on adjacent fuel elements, assuring minimal spacing and providing lateral support for the elements. Thin graphite discs 33, 43 serve as gaskets between the body section 13 and the reflectors 21, 23.
Patent GB-1010528-A (GB)
Title: Improvements in or relating to radiographic apparatus
Inventor: CONNELLY FRANK CECIL
IPC: H05G1/46
Filed: 1963-10-24
Abstract: 1,010,528. Control systems for X-ray apparatus. GENERAL ELECTRIC CO. Ltd. Sept. 24, 1964 [Oct. 24, 1963], No. 42013/63. Heading H2H. An overload protection arrangement for radiographic apparatus comprises a switch 1 for varying the voltage applied to the X-ray tube of the apparatus and a switch 2 for controlling the current through the tube, a flexible cable 6 being attached to the switches and arranged with a bight which passes over a pulley 7 carried by a spring-loaded arm 8, the position of which arm is determined by a cam 9 associated with the time exposure switch 10. Thus movement of the switch 10 causes the cable to be moved so as to operate the switches 1, 2 in opposite senses thus to prevent the current/voltage product from exceeding a maximum value for a given time exposure setting. In a further embodiment the switch 2 is arranged to be driven by an intermittent drive whereby the current is reduced in value by steps each time the switch 1 alters the voltage by a given amount.
Patent GB-1434405-A (GB)
Title: Phenyl-benzoic acid derivatives
IPC: A61K31/18
Filed: 1973-09-06
Abstract: 1434405 Phenyl-benzoic acids LEO PHARMACEUTICAL PRODUCTS Ltd AS 21 Aug 1974 [6 Sept 1973] 42050/73 Heading C2C [Also in Division A5] The invention comprises novel therapeutic compounds (I) in which R 1  represents an optionally substituted, straight or branched C 1 -C 6  alkyl, alkenyl or alkynyl radical, or a C 1 -C 3  alkyl radical substituted with phenyl, halophenyl, trifluoromethylphenyl, (C 1  to C 6  alkoxy)phenyl, or with a 5-membered or 6-membered heterocyclic ring containing not more than two heteroatoms selected from oxygen, sulphur and nitrogen; Ar stands for an optionally substituted phenyl radical; Y stands for O, S, NH or a CH 2  radical; and YR 1  is placed in the 2- or 3- position with respect to the -COOH group; and pharmaceutically acceptable, non-toxic salts and esters thereof. They are made by standard methods and many intermediates and starting materials are also prepared.
Patent GB-1270016-A (GB)
Title: Mushroom cutting apparatus
IPC: A23N15/04
Filed: 1969-04-15
Abstract: 1,270,016. Conveying mushrooms; shoots. AMERICAN MUSHROOM CO. 15 April, 1969 [18 April, 1968; 28 Feb., 1969], No. 42341/71. Divided out of 1,270,015. Headings B8A and B8S. [Also in Division A4] Apparatus for cutting mushrooms comprises means for receiving size-graded mushrooms in sequence cap-down, means 60, Fig. 5, for inverting each mushroom so that it is cap-up, an endless cutter conveyer 70, Figs. 5, 7, for receiving said inverted mushrooms, the top run thereof being generally horizontal and having a first series of stem-receiving openings 724 each formed by a substantially semicircular recess in each plate of one pair of a series of pairs of plates 720, 722 which support the mushroom caps, a slider plate 750 for maintaining the mushrooms in each opening along part of said top run at a predetermined elevation, and a stationary cutter located adjacent the top run of said conveyer 70 and immediately below the path of plates 720, 722 along said top run to cut off the roots of the mushrooms. The mushrooms may be oriented in a plurality of side by side rows cap downwards and uniformly fed in timed relationship with the other mushrooms in the same row by apparatus of the type disclosed in Specification 1,270,015, there being an equal plurality of side by side cavities 610 in the conveyer 60 for receiving the oriented mushrooms and transferring them one into each opening 724. The cutter conveyer 70 further comprises a series of pairs of plates 730, 732 similar to the plates 720, 722 and spaced from the plates 720, 722 by a distance approximately equal to the thickness of stationary knife blades 740, 742 which are mounted between these two series along the top run of conveyer 70. Plates 720, 722, 730, 732 are secured to conveyer chains via supports 718 and are spaced by members 734, Fig. 7. Two knife blades 740 are cantilevered from the side portions of conveyer 70 and their free ends are spaced apart to allow passage of members 734 therebetween. Two knife blades 742 are similarly mounted downstream of blades 740. The blades 740 cut off the mushroom root ends as these are supported by the adjustable height plate 750. Blades 742 cut off the stems as the caps are supported by plates 720, 722. The roots, stems and caps fall into containers 752, 756 and 760 respectively. Container 760 catches all water falling through the conveyer 70, a pump P pumping such water back to an upstream mushroom reservoir.
Patent GB-1361636-A (GB)
Title: Reactive trisazo and stilbenedisazo dyestuffs
IPC: C09B62/04
Filed: 1971-09-10
Abstract: 1361636 Trisazo and stilbene-azo dyes IMPERIAL CHEMICAL INDUSTRIES Ltd 27 July 1972 [10 Sept 1971] 42353/71 Heading C4P New trisazo and stilbene-azo dyes of formula wherein R 5  is a radical of formula n has the value 0 or 1, R 4  represents a monosulpho-m- or p-phenylene radical, R 3  and R 6  may be the same or different and each represents H or an alkyl or hydroxyalkyl group of 1-4 carbon atoms, R and R 8  may be the same or different and each represents a sulphonaphthyl or sulphophenyl radical which may be further substituted by CH 3 , OCH 3  or Cl, and R 1 , R 2  and R 7  may be the same or different and each represents a 1,4-phenylene radical which may be substituted by CH 3 , OCH 3 , Cl, SO 3 H, -NHCONH 2  or NHCOR 9  where R 9  is H or an alkyl group of 1-3 carbon atoms, or a 1,4-naphthylene radical which may be substituted by OCH 3  or SO 3 H, are prepared by condensing an aminostilbene or amino-azo dye derivative and an amino-disazo dye with cyanuric chloride. The dyes give brown shades on cellulose fibres by the usual reactive dyeing processes.
Patent GB-1528766-A (GB)
Title: Exposure control systems
IPC: G03B9/40
Filed: 1975-10-16
Abstract: 1528766 Shutter-diaphragm control WEST ELECTRIC CO Ltd 16 Oct 1975 [18 Oct 1974]  42391/75 Heading G2A A shutter-diaphragm is opened by a pulsed stepper motor 6 until the light intensity incident on a photo-cell 33 reaches a predetermined value, the photo-cell being located behind light control means 36 whose transmissivity is altered in correspondence with the opening up of the diaphragm. The light control means may comprise a supplementary aperture formed in the diaphragm blades or, as shown, an electro-optic element e.g. a liquid crystal, Kerr cell or electrically sensitive suspension. As shown, operation of the shutter release charges over a switch 30 to contact S2. This turns off a transistor 31 so that (a) pulses from a generator 32 can pass to a motor control circuit 22 to open up the aperture (b) a transistor 38 turns on whereby a capacitor 39 starts to discharge through a resistor 44. As the capacitor discharges the voltage across electro-optic element 36 gradually falls and so the transmissivity of the element 36 gradually rises. When the photo-cell is sufficiently illuminated, a transistor 35 conducts to stop the passage of pulses from generator 32 to control circuit 22. Thus further opening of the aperture is prevented. The blades are closed by a spring (36) Figs. 1A, B, C (not shown) when switch 30 is returned (by means not shown) to contact S1 to reset circuit 22. In Figs. 10, 11 (not shown) the voltage across element 36 is reduced in steps.
Patent GB-1059630-A (GB)
Title: Improvements in or relating to drilling a hole through a piece of glass
Inventor: CAMPBELL ARCHIBALD JAMES
IPC: B28D1/04
Filed: 1963-10-28
Abstract: 1,059,630. Drilling machine details. BEVERLEY TOOL & ENGINEERING CO. Ltd. Dec. 7, 1964 [Oct. 28, 1963], No. 42436/63. Heading B3C. A hole 5 is drilled through a sheet of glass 1 by rotating a drill (3), Figs. 3, 4 (not shown), to form an annulus (4), retracting the drill, and then drilling from the other side of the glass, by a second drill (2); the tool (3) being automatically operated when rotation of tool (2) commences. Drills (2) and (3) are carried in quills (17), (20), rotated by electric motors (19), (23), and the glass (1) is clamped on a table,(13) by a clamp (12). A cam (29) is rotated by an electric motor (31), and reciprocates a rod (27) connected to a horizontal arm (25), so that quill (20) along with tool (3) is moved vertically. Cutting fluid is supplied to the drills by cowls (6), (7) and is drained away at (22) for recirculation. Motor (19) is started by closing switch (38), which also starts motors (23), (31). Drill (3) is rotated and is raised by cam (29) to form annulus (4). The drill is retracted when cam portion (42) bears on the top of follower (28), Fig. 6 (not shown), and the cam actuates a micro-switch to switch off motors (23), (31). Drill (2) is now moved into the work to complete hole (5) by a handle (18). Clamp (12) is operated and the supply of water to cowls (6), (7) is provided, by operating a foot pedal. Rod (27) is connected to arm (25) by a nut (44) screwed on to the rod, a spring (45) seated in a bore (43) in the lever, a sleeve (46) screwed on to the nut, and a closed end sleeve (47) screwed to the rod. If the worn drill is not drilling, upward movement of rod (27) compresses spring (45) instead of actuating arm (25), and sleeve (46) moves upwardly to actuate a micro-switch to stop motors (23), (31). Sleeve (47) is adjustable, and abuts a stop to vary the depth of cut.
Patent GB-1283409-A (GB)
Title: Processes and apparatus for the preparation of intermediates of resins
IPC: B02C4/00
Filed: 1969-08-27
Abstract: 1283409 Mixing BUSS AG 27 Aug 1969 [13 Sept 1968] 42555/69 Heading B1C [Also in Division B5] A process for preparing thermosetting resin intermediates comprises feeding one or more resin precursors together with a hardener and any other ingredients to a screw extruder I, mixing and kneading the ingredients in the extruder whilst heating or cooling to plastify the mix, extruding the mix through die 5 to a cooling zone 7 to solidify the mix, and grinding the solidified mix to powder in a mill 10. The extruder may be provided with a screw having interrupted flights and executing a rotational and reciprocating movement in a barrel provided with kneading teeth. Both screw and barrel may be provided with means for circulation of heat transfer fluid. The cooling zone may have two sections, the first section comprising an endless belt 8 and pre-forming rolls and the second section comprising endless belt 8' and crushing rolls 12. Belt 8 may be made of stainless steel having a highly polished surface to prevent sticking of the resin intermediate thereto. In use, the solidified resin intermediate is reduced by rolls 11, 12 to a size suitable for feeding to the grinding mill 10.
Patent GB-1284169-A (GB)
Title: Non-return valve
Inventor: GERDTS HERBERT RUDIGER
IPC: F16K15/14
Filed: 1970-09-04
Abstract: 1284169 Valves H R GERDTS and W F GERDTS [trading as GUSTAV F GERDTS KG] 4 Sept 1970 [4 Sept 1969] 42565/70 Heading F2V A non-return valve comprises a metallic tubular body 1, an annular plastics member 4, 6 at each end of the body 1 held thereto by collars 2, 3, and a valve disc 9 made of plastics material urged towards a seat 5 by a spring 14. The valve disc 9 carries stroke-limiting projections and guide ribs 11. The annular members 4, 6 may alternatively be adhered to the body 1.
Patent GB-1317848-A (GB)
Title: N-thienylalkyl-beta-alkoxy-trifluoromethylphenalkylamines
IPC: C07D333/20
Filed: 1971-09-14
Abstract: 1317848 Trifluoromethylphenalkylamines SMITH KLINE & FRENCH LABORATORIES 14 Sept 1971 [14 Sept 1970] 42680/71 Heading C2C Novel compounds of Formula (I): in which R is C 1-3  alkyl, R 1  is H or CH 3 , R 2  is H or C 1-3  alkyl, and A is a C 1-3  straight or branched alkylene chain, and their pharmaceutically acceptable acid addition salts, may be obtained by reacting an appropriate trifluoromethylsubstituted #-alkoxyphenalkyl halide, preferably the bromide, with an appropriate thienylalkylamine. Salts may be obtained by known methods and racemic mixtures may be separated into d and l isomers. Pharmaceutical compositions having anorectic activity comprise a compound of Formula (I) above together with a pharmaceutical carrier, preferably in forms suitable for administration orally or parenterally.
Patent GB-1024259-A (GB)
Title: A device for measuring the average values of pulse height of a number of successive light pulses
IPC: G05B11/01
Filed: 1962-11-14
Abstract: 1,024,259. Photo-electric turbidity measurement. LICENTIA PATENT-VERWALTUNGSG.m.b.H. Nov. 14, 1962 [Nov. 14, 1961], No. 43064/62. Heading G1A. To measure atmospheric turbidity brief pulse of light are directed from a source on to a photodiode 10 and via atmosphere to be investigated to photo-diode 11. Electrical signals comprising brief pulses proportional to the difference in amplitude of the two photo-diode outputs are amplified, passed through a gate only open when the light source is being pulsed, and fed to seperator 15. This sorts positive and negative going pulses respectively to pulse lengtheners 17 and 18 which may increase the pulse lengths 10<SP>5</SP> times. The stages 17 and 18 feed an integrating stage 20 which combines and smoothes their outputs to provide a signal applied to magnetic amplifier 20 to control adjusting means 21 modifying the position of a grey wedge 22 in the light path to detector 10. The system controls the grey wedge to balance the light received by the detectors, the position of the wedge being a measure of atmospheric turbidity. The photo-electric system may be used to measure the intensity of any series of brief light pulses by comparison with a series of similarly timed reference pulses.