baber/WOPTO huggingface dataset:
Patent GB-1395530-A (GB)
Title: Integral microporous high void volume polycarbonate membranes and a dry process for forming same
IPC: C08J9/28
Filed: 1972-10-18
Abstract: 1395530 Polycarbonate membranes CHEMICAL SYSTEMS Inc 18 Oct 1972 [18 Oct 1971] 47985/72 Heading B5B [Also in Division C3] Integral ultra- and micro-filtration membranes having a void volume greater than 50% are prepared from a polycarbonate or polycarbonate-polyalkylene oxide copolymer having a M.W. greater than 46,000 (e.g. up to 145,000), by a dry phase inversion process in which a solution of the polymer containing 3-10g. of polymer per 100 ml. of solution and including a swelling agent and a wetting agent is cast on a substrate and allowed to evaporate until the membrane is completely dry. The polymer is preferably a polycarbonate resin having the general formula wherein n is an integer between 180 and 600; x is an integer between 180 and 600; y is an integer between 1 and 6; z is an integer between 13 and 450; R is H-, (CH 3 ) 2 CH- or Ph-; R<SP>1</SP> is or a substituted derivative thereof; and R<SP>11</SP> is -CH 2 -CH 2 -, -CH 2 -CH(CH 3 )- or -[CH 2 CH 2 O] a -[CH(CH 3 )-CH 2 O-] c -[CH 2 CH 2 O] b  where a and b are integers between 3 and 10 and c is an integer between 20 and 50. The casting solution solvent is preferably CH 2 Cl 2 , CHCl 3 , bis-dichloroethylene, MEK, THF, dioxane or mixtures thereof. The swelling agent is preferably resorcinol, trifluoroethanol, cyclohexanol, hexafluoroisopropanol, the hemiacetal formed by reaction of methanol with hexafluoroacetone or mixtures of one of the above with isopropanol. Suitable wetting agents are the non-ionic surfactants. In examples copolymers having M.W. within the stated range are prepared by reaction of methylene chloride/ pyridine solutions of bisphenol A and polyethylene oxide, polypropylene oxide or polyethylene oxide end-blocked polypropylene oxide with phosgene. The resultant copolymers and bisphenol A polycarbonate homopolymer are dissolved in casting solutions containing one of the above swelling and wetting agents, cast on to glass plates and allowed to evaporate to dryness.
Patent GB-1492182-A (GB)
Title: Process for fluidised contact
IPC: B01J8/22
Filed: 1974-11-06
Abstract: 1492182 Fluidized beds for treating oils NIPPON OIL CO Ltd 6 Nov 1974 [7 Nov 1973 25 Sept 1974] 48087/74 Heading C5E [Also in Division B1] A process for bringing about the fluidized contact of a fluid, which consists of a liquid or a mixture of a liquid and a gas, with solid particles in a contacting vessel, comprises forming a bed of a porous packing material in at least part of a contact zone of the contacting vessel, accommodating the solid particles in a lower part of the contact zone, introducing the fluid from the bottom of the contacting vessel to form a fluidized layer of the solid particles within the contact zone, and withdrawing the fluid which has made contact with the solid particles from the upper part of the contacting vessel, in which process: the ratio of the superficial volume occupied by the bed of porous packing material to the real volume of the porous packing material is at least 1À3 : 1, and the ratio of the average diameter of the pores of the porous packing material to the average diameter of the solid particles is from 1À1 : 1 to 10 : 1. The porous material may be metal, porcelain clay, silica, alumina, magnesia, polyethylene, polypropylene, pvc, or ptfe. In all the examples the solid particles comprise a catalyst and the liquid a hydrocarbon oil; there are examples of hydrogenation over Co-Mo on silica-alumina, purifying naphtha over molecular sieve, hydrogenating naphtha over molecular sieve, hydrodesulphurization of residual oil over Co-Mo on silica-alumina, and an unspecified treatment of kerosene in the presence of nitrogen over Co-Mo on silica-alumina.
Patent GB-1331948-A (GB)
Title: Regeneration of ion exchange resins
IPC: C05B7/00
Filed: 1970-10-09
Abstract: 1331948 Regenerating Ion-exchange resins INSTITUTUL DE PROIECTARI PENTRU INDUSTRIA OHIMICA ANORGANICA SI A INGRASAMINTELOR 9 Oct 1970 [11 Oct 1969] 48135/70 Heading B1J [Also in Division C1] Cationic or anionic ion-exchange resin beads are regenerated with relatively concentrated acid or base respectively, the temperature volume and rate of flow of the regenerant and the thickness of the resin layer being such that the temperature at the surface of he resin beads does not exceed 20‹C. Under these conditions, the resin does not deteriorate excessively. Sulphonated styrene-divinyl-benzene macroporous resins are particularly resistant, especially when sulphonation has been carried out at not more than 100‹C, and regeneration may be effected with 50% nitric acid. Regeneration may take place in the annular space between perforated tubes 1 and 4, lined with metal screens 9, in a vessel 2. The resin is hydraulically loaded through an inlet b and the carrier liquid is removed through an outlet c by vacuum. The regenerant is introduced through inlets a 1 , a 2  and subsequently removed through outlet c. Remaining traces may be removed by suction or, through an outlet d, by blowing in air or inert gas, and then by rinsing with demineralized water introduced through the inlets a 1 , a 2 . Regenerated resin is returned to the ionexchange reactor through the inlet b by the introduction of water and air through outlets d and c. A complete apparatus is described, Fig. 3 (not shown), for removal of ammonium cation and nitrate anion using separate cation and anion exchange reactors (4 1  and 4 2 ) and a final mixed-bed reactor (7). The two main reactors are each associated with a regenerating apparatus (9 1  and 9 2 ) as shown in Fig. 2, the regenerants being 56% nitric acid and 10-20% ammonia solution respectively. The use of this apparatus for the treatment of condensates in the production of ammonium nitrate and in the production of complex fertilizers by the Norsk-Hydro process is also described (see Division C1).
Patent GB-1214554-A (GB)
Title: Improvements in and relating to the fireproofing of polyamide shaped articles
IPC: D01F9/30
Filed: 1968-10-11
Abstract: 1,214,554. Carbon fibres. MONSANTO CO. 11 Oct., 1968 [12 Oct., 1967], No. 48339/68. Heading C1A. [Also in Division D1] Aromatic polyamide material which has been flame-proofed by reaction with the vapour of a halide or oxyhalide of carbon, phosphorus or sulphur (see Division D1) may be heated to effect carbonization without change of physical form. The particular physical forms exemplified are fibres and fabrics.
Patent GB-1429459-A (GB)
Title: Process for the production of metal-plated fibres
IPC: D06M11/83
Filed: 1974-11-08
Abstract: 1429459 Electroless plating of fibres KURARAY CO Ltd 8 Nov 1974 [30 Nov 1973] 48461/74 Heading C7F Fibres of e.g. polyester, polyamide, polyolefin, polyvinyl alcohol, polyacrylonitrile, acetate, rayon, cotton or wool are electrolessly plated with e.g. Ni, Cu, Co-Ni, Cr or Sn by activating with stannous and palladium chlorides and then projecting the electroless solution at a space velocity of 100 to 600m<SP>3</SP> of the plating solution per m<SP>3</SP> of the fibres per hr. against the fibres which have an areal weight of 0À5 to 5À0 kg/m<SP>2</SP>. Baths are disclosed including a Cu bath comprising CuSO 4 5H 2 O. 17À5g/l., KNa C4H4 O 6 . 4H 2  O 85g/l., NaOH 25g/l., mercaptobenzthyazole 15 mg/l., CH 2 O (36%) 25ml/l.
Patent GB-1153235-A (GB)
Title: An Outer Casing for an Hydraulic or Pneumatic Telescopic Unit
IPC: F16J10/02
Filed: 1967-10-26
Abstract: 1,153,235. Shock absorber casing. REICHE & CO. 26 Oct., 1967 [26 July, 1967], No. 48697/67. Heading F2S. The tubular outer easing of a shock absorber has an end wall 1 formed by a non-cutting forming operation, with the wall thickness adjacent said end wall increasing continuously or in stages towards said end wall. The other open end 3 preferably has an increasing wall thickness and is softer than the remainder of the tube. A suspension eye finally closes the end wall 1, by being welded thereto.
Patent GB-1526068-A (GB)
Title: Flame retardant compositions
IPC: C08L27/00
Filed: 1975-11-27
Abstract: 1526068 Fire-retarding polyphenylene ether resin or ABS compositions GENERAL ELECTRIC CO 27 Nov 1975 [6 Dec 1974] 48790/75 Headings C3P and C3R A thermoplastic moulding composition comprises, per 100 parts by weight of the total composition, 10-95 parts by weight of a normally flammable polyphenylene ether resin or an acrylonitrile-butadiene-styrene or acrylonitrilebutadiene-alpha-methyl styrene copolymer; 2- 25 parts by weight of a flame retardant additive, and 0À1-3 parts by weight of a polytetrafluoroethylene resin. The polyphenylene ether resin may be admixed with a vinyl aromatic resin of which many examples are given. Specific Examples describe compositions containing poly (2,6-dimethyl-1,4-phenylene ether), rubber modified polystyrene, PTFE and polyethylene and either a mixture of:-tetrabromobisphenol-A, triphenylphosphate, antimony oxide; a mixture of hexabromobenzene, triphenyl phosphate and antimony oxide; or triphenylphosphate. Other examples describe compositions containing ABS polymer, PTFE, and as fire-retardant a Diels-Alder adduct.
Patent GB-1288210-A (GB)
IPC: B61G1/18
Filed: 1970-10-15
Abstract: 1288210 Rotary dump couplers for rail vehicles AMSTED INDUSTRIES Inc 15 Oct 1970 [6 Nov 1969] 49085/70 Heading B7T A rail vehicle rotary dump coupler assembly comprises a coupler 10 engaged by way of its shank 12 in a yoke 14 containing within its upper and lower straps 56, 48 draft gear 64 and a front follower 60, the butt end 30 of the shank 12 at its rear end abutting the follower through spherical surfaces 70, 68 having point 72 as their centre, and the front end of the butt having upper and lower spherical surfaces 32, 34, having point 40 as their centre, engaged with corresponding surfaces 36 and 38, on the yoke. Stops 104, 106 on the straps, and stops (not shown) on follower 16 prevent squeezing of the butt during operating conditions. The butt is located in the yoke by retaining keys (86), 88. Feet of the keys slide on a retaining plate 22 and spherical surfaces on the keys correspond to surfaces 36, 38 and are engaged by surfaces 32, 34 during rotation of the coupler. Surfaces 54 and 58 of the yoke are cylindrical and are adapted to be contacted by spherical surface 52 and cylindrical surface 46 of the butt.
Patent GB-1119652-A (GB)
Title: Supply cart
Inventor: PROPST ROBERT LEWIS
IPC: B62B3/16
Filed: 1965-03-17
Abstract: 1,119,652. Hand trucks. HERMAN MILLER Inc. 17 March, 1965, No. 49088/66. Divided out of 1,119,651. Heading B7B. A hand truck has a number of rails 35 extending across the front face of the truck to support suitably shaped containers and a rail 36 which nests in the rail 35 of another truck to form a stack. The truck is moulded from steam-resistant plastics material.
Patent GB-1277463-A (GB)
Title: Textile staple fibers and a method for manufacturing the same
IPC: D01F6/62
Filed: 1969-10-07
Abstract: 1277463 Crimped staple fibres for open-end spinning TORAY INDUSTRIES Inc 7 Oct 1969 [9 Oct 1968] 49121/69 Headings D1F and D1W Crimped synthetic staple fibres satisfying the criterion set out below are subjected to openend spinning. The fibres should have properties satisfying the following inequality:- 1.6 x 10<SP>-1</SP> (Cn - 12.5)<SP>2</SP> + 1.1 x 10<SP>-1</SP> (Ci-11)<SP>2</SP> + 3.27 x 10<SP>-3</SP> (Cr-52.5)<SP>2</SP> + 6.25 x 10<SP>2</SP> (Á s -0.36)<SP>2</SP> + 6.25 x 10<SP>2</SP> (Ád-0.28)<SP>2</SP><1 wherein: Cn is the number of crimps per 25mm under 2mg per denier tension; Ci is the percentage extension on an increase in tension from 2mg to 50mg per denier; Cr is the percentage recovery of that extension on return to 2mg per denier tension after 30 minutes extension and 2 minutes recovery, and Ás and Ád are respectively static and dynamic frictional coefficients of the fibre. Suitable polyester staple fibres may be produced by heatsetting in the temperature range 100‹ to 115‹C after crimping.
Patent GB-1466404-A (GB)
Title: Egg sorting apparatus responsive to the weight of eggs
IPC: A01K43/00
Filed: 1974-11-14
Abstract: 1466404 Reciprocating carriers; suction heads BIG DUTCHMAN (INTERNATIONAL) AG 14 Nov 1974 [15 Nov 1973] 49378/74 Headings B8A and B8H [Also in Divisions G1 and G3] An egg sorting apparatus comprises a weighing means 1, and a conveyer for carrying a weighed egg to a collector having apertures 66, the conveyer including a frame 13 movable backwards and forwards along the conveyer, a suction cup 14 for holding the egg, a bellows 15 for producing suction in the cup, and a lifting frame 38 for lowering an egg to be weighed on to the weighing means and for lifting a weighed egg into abutment with the cup. Conveyer frame 13 is reciprocated along rods 30, 31 by means of a chain 36 passing around sprockets 54, 69 and a pair of legs 77 which are linked at one end to the chain and at the other end are mounted on a shaft 67 movable in a slot 65 of the frume. When the legs 77 are being carried around sprocket 54, the frame is stationary, and a sprocket 33 attached to one of the legs drives a further sprocket 25 attached to cam 18, Figs. 1, 2, 3. Cam 18 acts on a pin 12 mounted on an arm 73 to raise the arm about its pivot 74, and raising of arm 73 extends the bellows 14 to induce suction in cup 15. At the same time a cam 48, Fig. 5 acts on a lever 55 coupled via a rod 56 with the lifting frame 38 to cause the latter to raise a weighed egg into abutment with the cup 15. A cam disc 51 actuates a microswitch 52 which causes electromagnet 16 to be actuated to maintain arm 73 in its raised position. When the egg is over the appropriate aperture 66, a pin 23 engages a microswitch associated therewith which has been activated by the weighing means, and the electromagnet 16 is deactivated, allowing arm 73 to fall and the egg to drop through the aperture. A further cam 49 controls a microswitch 51 which controls the speed of the motor 60 driving the chain 36 such that it moves at double speed during that part of a cycle in which it is not carrying an egg.
Patent GB-1245778-A (GB)
Title: Process for the production of aldehydes
IPC: C07C45/50
Filed: 1968-10-18
Abstract: 1,245,778. Oxo process. RUHRCHEMIE A.G. 18 Oct., 1968 [7 Nov., 1967; 2 Sept., 1968], No. 49619/68. Heading C2C. Aldehydes are prepared by the reaction of olefinic compounds with CO and H 2  at elevated temperature and pressure in the presence of a Group VIII metal catalyst and of a 1,2-diphosphacyclopent - 5 - en - 4 - one compound of formula where R 1  to R 6  are independently unsubstituted or substituted aliphatic, cycloaliphatic, heterocyclic or aromatic radicals, A 1  and A 2  are similar or different bridge atoms selected from oxygen, sulphur and nitrogen and n is 0 or 1 or may be 2 when the bridge atom is sulphur or nitrogen. An alkali metal hydroxide and/or tertiary amine may also be present. Examples relate to the hydroformylation of hexene-1 and propylene.
Patent GB-1407298-A (GB)
Title: Filtering element
IPC: B01D29/00
Filed: 1972-10-30
Abstract: 1407298 Filter element PRZEDSIEBIORSTWO PROJEKTOWANIA I DOSTAW KOMPLETNYCH OBIEKTOW PRZEMYSLOWYCH CHEMADEX 30 Oct 1972 [28 Oct 1971] 49910/72 Heading B1D An apertured pipe 1 is enclosed by a stack of externally grooved ceramic or plastics sleeves 4 with apertures (not shown) in their grooves, and a filter cloth tube 11 is stretched over the sleeves between end clamps 10, 12 and 10a, 12a, each comprising resiliently lined and covered rings and seats. The tube 11 may be tensioned by rotating bolt 8, 19 to move slider 7 axially out of sleeve 5. Screw 6 prevents slider 7 from rotating. Filtration flow is inwards and tube 11 is cleaned by backwashing and simultaneous vibration.
Patent GB-1220921-A (GB)
Title: Improvements in or relating to space heating apparatus
Inventor: SMITH CHARLES AQUILA VINCENT
IPC: F24C7/00
Filed: 1966-11-08
Abstract: 1220921 Reflectors for space-heating apparatus C A V SMITH 8 Feb 1968 [8 Nov 1966] 49982/66 Headings F4V and VB2A [Also in Division H5] In space-heating apparatus which includes a shell 10 having an opening 9 for the emission of heat and which contains at least one source of heat situated with a reflector 11, the reflector comprises inclined rear and top panels 12, 13, a horizontal base panel 14 and an upwardly extending front portion 15, said source of heat being located behind said upward portion, the said panels forming the reflector being dimpled either irregularly or in a regular pattern. The reflector also includes two side panels, Fig.2 (not shown), diverging towards the front of the shell 10. As shown, the heating apparatus includes two horizontal electric elements 19 and 20 disposed one above the other in the reflector, an electric fan 22 with a block heat element assembly 23 located above the reflector so as to discharge hot air through the opening 9, and a grill fitted over the opening 9 to protect said elements.
Patent GB-1306898-A (GB)
Title: Loudspeaker arrangement in a vehicle
IPC: B60R11/00
Filed: 1971-10-29
Abstract: 1306898 Sun-visors DR-ING hcF PORSCHE KG 29 Oct 1971 [29 Oct 1970] 50437/71 Heading B7J [Also in Division H4] A loud-speaker 14 (Fig. 2) is arranged in a vehicle's sun-visor 4 (Fig. 1) constructed as a flat padded member pivotally mounted on the vehicle body 12 in the interior of the vehicle. Sound emission preferably takes place through openings on both sides of the sun-visor 4. The sun-visor includes a wire frame 5 surrounded by a foamed polyurethane body 6 and has a perforated cover 7. It is secured at one end by a spherical bearing 10 which permits universal movement. Its other end has a pin 9 removably secured in a U-shaped bearing 11. The wire frame 5 is connected to the loud-speaker frame 18 at four corners by metallic springs 19. Two such sun-visors 4, 4<SP>1</SP> carrying loud-speakers 14, 14<SP>1</SP> may be mounted adjacent the windscreen 2, between a mirror 3, to provide a stereophonic arrangement. The visors 4, 4<SP>1</SP> may be pivoted upwards against the roof (Fig. 3, not shown). In other stereophonic arrangements two visors are adjacent the rear window or adjacent opposite side windows.
Patent GB-1115786-A (GB)
Title: Uracil compounds and their use as herbicides
IPC: C07D401/04
Filed: 1965-12-01
Abstract: The invention comprises uracils of the formula <FORM:1115786/C2/1> where AN- is a cycloimino group containing 2-14 carbon atoms and at most 3 hetero atoms, X is oxygen or sulphur, R1 is hydrogen, chlorine, fluorine, bromine, iodine or a nitro, C1- 4 alkyl, C1- 4 alkoxy, hydroxymethyl or C2- 5 alkoxymethyl group, R2 is a C1- 3 alkyl group and R3 is hydrogen or a C1- 3 alkyl group or R1 and R2 together form a radical -(CH\2)n-, where n is 3, 4 or 5, and the salts and complexes of such uracils.  The uracils are prepared by condensing an appropriately substituted urea with an a -substituted-b -keto ester, treating the resulting ureido compound with a base, followed by acidification to separate the uracil.  If a b -keto-ester unsubstituted in the a -position is used, the resulting uracil can be converted to the required 5-substituted compound using conventional chlorination, bromination, iodination, nitration, formylation and alkylation processes.  The 4-thiouracils can be made by treating the corresponding di-oxo compounds with phosphorus penta-sulphide. The salts and complexes may be those formed with inorganic or organic bases or acids and phenols.  A large number of compounds are specified including those in which the cycloimino group is a hexahydro-1-azepinyl, morpholino, piperidino, 1-pyrrolidinyl, 10-phenothiazinyl, dihydro-1,3,5-dithiazin-5-yl, 1-aziridinyl, 1,2,3,6 -tetrahydro - 1 - pyridyl, 1 - piperazinyl, 9 - carbosolyl, 4 - pyrazolin - 1 - yl, tetrahydro - 1,4 - thiazin - 4 - yl, dihydro - 1,3,5dioxazin - 5 - yl, 1,2,3,4 - tetrahydro - 2 - isoquinolinyl, 3 - azabicyclo(3.2.2)nonan - 3 - yl, 1 - benzimidazolyl and 4 - pipecolin - 1 - yl group.  The uracils are used as herbicides (see Division A5).ALSO:Herbicidal compositions comprise uracils of the formula <FORM:1115786/A5-A6/1> where A \s6 N is a cycloimino group containing 2-14 carbon atoms and at most 3 - hetero atoms, X is oxygen or sulphur, R1 is hydrogen, chlorine, bromine, fluorine or iodine or a nitro, C1-4 alkyl, C1-4 alkoxy, hydroxymethyl or C2-5 alkoxymethyl group, R2 is a C1-3 alkyl group and R3 is hydrogen or a C1-3 alkyl group, or R1 and R2 together represent - (CH2)n - where n is 3,4 or 5 and salts and complexes of such uracils.  In addition to the usual diluents and additives the compositions may include other herbicidal compounds.  A large number of known herbicides are specified and include substituted ureas, substituted triazines, phenols, carboxylic acids and salts, esters, amides, hydrasides and nitriles thereof, thiolcarbamates, inorganic salts, mixed inorganic/organic salts, amines, quarternary ammonium compounds, other substituted uracils and chlorinated ketones.  Examples 262-273 relate to the preparation and application of the uracil composi. tions.
Patent GB-1017790-A (GB)
Title: Improvements in or relating to telecommunications systems
IPC: H04Q3/00
Filed: 1964-12-15
Abstract: 1,017,790. Automatic exchange systems. SIEMENS & HALSKE A.G. Dec. 15, 1964 [Dec. 16, 1963], No. 51299/64. Heading H4K. In a network such as the German national trunk dialling network in which exchanges are arranged in a top rank A, one or more intermediate ranks B and a bottom rank C, those in the ranks B, C being grouped, in order to assist routing, all the exchanges in the ranks B, C are connected to two exchanges of the next higher rank.
Patent GB-513383-A (GB)
Abstract: 513,383. Melamine. SOC. OF CHEMICAL INDUSTRY IN' BASLE. July 20, 1938, No. 21544. Convention date, July 24, 1937. [Class 2 (iii)] Melamine is prepared by heating dicyandiamide and liquid ammonia at a temperature not exceeding 100‹C., the amount of ammonia present being less than is necessary to dissolve completely the dicyandiamide at room temperature. According to the example, 3 parts by weight of dicyandiamide and 1 part by weight of liquid ammonia are heated for 6 hours at 100‹C. in a rotary autoclave ; the product contains about 55 per cent. melamine. By prolonging the reaction, higher yields are obtained, e.g., 70 per cent. after 18 hours.
Patent GB-1128458-A (GB)
Title: Variable gain equalizing networks
Inventor: FRIEND JOSEPH JOHN
IPC: H04B3/14
Filed: 1965-12-06
Abstract: 1,128,458. Transistor amplifying circuits; equalizer networks. WESTERN ELECTRIC CO. Inc. 6 Dec., 1965 [7 Dec., 1964], No. 51614/65. Headings H3T and H3U. An adjustable attenuation equalizer network comprises a one-port bridge network, e.g. N1, consisting of two arms Rc, Rd, including a potentiometer Rd, a further two arms Ra, Rb in parallel with the firstmentioned two arms, and a reactive connection, i.e. capacitor C 1 , from the tapping point of the potentiometer to the junction between the further two arms Ra, Rb. The bridge is such as to have a substantially constant D.C. impedance and an impedancefrequency characteristic including a break point, the A.C. impedance being adjustable by means of the potentiometer without substantially altering the frequency at which the break point occurs. While the bridging element has been shown as a capacitor C 1 , a network comprising resistance, capacitance and inductance may be utilized instead. A variable gain attenuation equalizer comprises a two-stage amplifier, e.g. stages A 1 , A 1 <SP>1</SP> having from the second stage A 1 <SP>1</SP> to the first A 1  a feedback network comprising a bridge network, e.g. N1, of the type described. As shown, the network N1 is connected in the emitter circuit of the first amplifier stage, and feedback from the output of the second stage A 1 <SP>1</SP>, which comprises a Darlington pair, is over resistor Rf. Further equalization is obtained by means of a network N2 of the type described connected between the stage A 1 <SP>1</SP> and a subsequent stage A 2 . A number of such amplifiers may be connected in cascade, the capacitors C 1  &c. being so proportioned that each subsequent stage corrects for a further frequency range over and above that corrected by preceding stages.