978,143. Electric meters; electric bridge circuits; liquid level measuring apparatus; indicating apparatus. BENDIX CORPORATION. March 14, 1963 [March 26, 1962], No. 10212/63. Headings G1J, G1N, G1Q and G1U. [Also in Divisions G4 and H3] The output voltage of a capacitive liquid level measuring bridge uses a circuit comprising a number of transistors of opposite conductivity type are arranged in cascade such that as the D.C. input signal rises the output voltage first rises and then falls. Fig. 1 comprises two such cascades in succession so that the final output voltage rises and falls twice. It is explained mathematically that so long as the signal voltage is below the level at which the respective output transistors 59 and 72 saturate the gain of each circuits is 2 but when they saturate the output voltage (e.g. E2) is related to the input voltage (e.g. E 1 ) by the relation E 2 = V - 2E 1 where V is the supply voltage. The circuit is used to measure the voltage from a liquid level indicator Fig. 3. The liquid level measuring capacitance 81 is connected in a capacitive bridge fed with alternating current from source 84 and having its output amplified at 85 rectified at 86 and 90 and then applied across a potential variable capacitor 83 in the form of a semi-conductor diode so as to balance the bridge, isolating chokes being provided to separate the A.C. path from the D.C. path. Rectified output from the amplifier is fed to a first meter 93 calibrated in metres and through a folding circuit similar to Fig. 1 to a meter 95 calibrated in decimetres. As the level of the liquid rises from 0 to 1 metre the pointer of meter 93 moves clockwise from 0 to 1 and the pointer of 95 moves in clockwise direction from 0 to 10. A further rise of 1 to 2 metres increases the reading on 93 from 1 to 2 but, as the output of the folding-circuit is now falling, causes the pointer of meter 95 to rotate in an anticlockwise direction towards its initial position, readings being taken from the inner scale. Further rise from 2 to 3 metres causes the pointer of metre 95 to move clockwise again while the rise from 3 to 4 metres causes pointer of metre 95 to return in an anticlockwise direction.

At least part of a readout pattern including carrier collecting electrodes, capacitors, thin-film transistors, data lines and gate lines is formed by vapor deposition or printing. This is formed separately from a semiconductor thick film. The semiconductor thick film and readout pattern constitute a flat panel X-ray detector (FPD) is mounted in a case to form a unit. A weight reduction is achieved by using the semiconductor thick film in place of a conventional glass substrate. The FPD manufactured in this way is free from great restrictions in time of transport and use.

1,020,974. Magnetic tests. SIEMENSSCHUCKERTWERKE A.G. Oct. 26, 1964 [Oct. 26, 1963], No. 43638/64. Heading G1N. [Also in Division H1] An indication of the gradient of a magnetic field is given by a meter 9 connected across a bridge circuit containing two probe arms 1, 2 joined by a bridge 18, the probe arms and the bridge being formed integrally from a single piece of magneto-resistive semi-conductor material, such as indium antimonide. The bridge 18 is metallized, and mutually parallel strips of good conductivity may be mounted on or embedded in the probe arms 1, 2 at right angles to their axes. Two such devices, possibly formed from a single piece of semi-conductor material, Fig. 4 (not shown), may be combined to measure the second derivative with respect to distance of the magnetic field.

486,851. Telescopes. REASON, R. E., and KAPELLA, Ltd. Dec. 11, 1936, Nos. 30740/36 and 663/38. [Class 97 (i)] In a sighting telescope, particularly for measuring the angular or lateral displacement of a member by observing the displacement of the image of a mark &c. formed by an objective in the telescope, the observing system is provided with means for reversing the displacement of one portion of the image relatively to that of the other portion and means are also provided in the telescope whereby the two portions are brought into superposition or into alignment with one another. Fig. 1 shows a form in which the mark is within the telescope and consists of a slit D illuminated by a lamp C and condenser C<1>. The rays are directed along the axis of the telescope by a thin film E constituting a semi-transparent mirror. The optical distance from the slit to the telescope objective A is equal to the focal length of the objective so that the rays on emerging from the objective are parallel. These rays are received by a mirror F on the member whose angular position is to be measured and are returned through the objective to form an image in the focal plane. In this plane the rays are divided, for example by a pair of segmental lenses G<1>, G<2>, and the two beams pass to an objective H having its principal focus in the plane of the image, and thence through apertures J<1>, J<2> in a screen J to an objective H<1> forming a second image, the beams being recombined at such image by a biprism K and transmitted to an eyepiece K<1>. Between the objectives H, H<1>, one of the beams passes through a reversing prism L<1> and the other beam passes through a glass block L to equalize the ray paths. To bring the two half images into alignment, a prism M displaceable along the axis of the telescope is provided, this prism being provided with a pointer M<1> which indicates on a scale M<2> the displacement of the mirror F. Instead of an auto-collimating telescope as above described, a focusing telescope as in Fig. 3 may be used in conjunction with a sighting mark on the object whose displacement is to be measured. In Fig. 3, the whole of the ray-dividing and observing system is mounted in a tube S which can be moved axially for focusing by a rack S<1> and pinion S<2>. To prevent lateral errors in the focusing movement the tube S is mounted in the tube B in two bearing rings T having sharp-edged recesses T<1>, Fig. 4, constituting a four point support, against which the tube is pressed by springs U acting through balls U<1>. To enable this instrument to be used alternatively as an auto-collimating telescope, a slit D and lamp C may be provided. Specification 430,761 is referred to.

At least part of a readout pattern including carrier collecting electrodes, capacitors, thin-film transistors, data lines and gate lines is formed by vapor deposition or printing. This is formed separately from a semiconductor thick film. The semiconductor thick film and readout pattern constitute a flat panel X-ray detector (FPD) is mounted in a case to form a unit. A weight reduction is achieved by using the semiconductor thick film in place of a conventional glass substrate. The FPD manufactured in this way is free from great restrictions in time of transport and use.

942,609. Radiographic techniques. UNITED KINGDOM ATOMIC ENERGY AUTHORITY. July 19, 1962 [Aug. 25, 1961], No. 30703/61. Heading H5R. A method for the radiographic examination of materials having low absorption coefficients comprises contacting the parts to be examined with a volatile radiopaque fluid whose linear absorption coefficient is greater than twice that of the material of the specimen, effecting radiography, and removing the fluid by heating. The method may be applied to beryllium, beryllia or graphite which are commonly used in nuclear reactors, and the liquid, which may be applied by dipping, vacuum impregnation or vapour phase contacting, is a halogensubstituted aromatic or aliphatic hydrocarbon, e.g. carbon tetrachloride, bromobenzene, tetrabromethane or perchlorethylene. Removal of the halogen compounds below a level of 10-20 p.p.n. is effected by a simple treatment in a vacuum furnace at 95‹ C. for 30 hours, or at 400‹ C. for 2 hours. To detect microcracks, a thin film of the liquid is trapped over the surface of the specimen by using a transparent impermeable envelope, e.g. Cellophane (Registered Trade Mark).

1,059,074. Semi-conductor devices. WESTERN ELECTRIC CO. Inc. March 24, 1964 [March 29, 1963], No. 12303/64. Heading HIK. A piezo-resistive strain gauge comprising a wafer of semi-conductor material having a cubic crystal structure is made insensitive to transverse and shear strains by choosing the orientation of the plane of the wafer in relation to the crystal lattice according to one of three given formulµ which express this orientation in terms of the piezo-resistive and compliance coefficients of the material. One of the formulµ relates to current measurement in the plane of the wafer and the other two relate to current measurement perpendicular to this plane. Specific examples are given for N and P type germanium, silicon, and lead telluride.

1,246,432. Polarizing apparatus. MULLARD Ltd. March 24, 1970, No. 14212/70. Heading G2J. [Also in Division G1] A temperature indicating device comprises a body 1 of birefringent material the birefringence of which varies with temperature, the body having both a polarizing layer 2 and a reflective surface 3 disposed on opposite surfaces thereof. In use, the body 1 which may be a single crystal of barium strontium niobate in the form of a thin film is located in an environment the temperature of which is required and a parallel beam of white light 4 is directed to the body through a window defined on one side of the body. The colour of the output beam 6 from the device is observed and such colour is indicative of the temperature of the environment in which the device is located. The polarizing layers 2 which may be provided with or separate from the reflective surfaces 3 may be of plastics material.