1,005,343. Wave guide switches. ALBISWERK ZURICH A.G. Feb. 15, 1963 [Feb. 16, 1962], No. 6153/63. Heading H1W. [Also in Division H4] A single antenna is coupled to both a transmitter and a receiver via impedance transforming networks which contain semi-conductor diodes acting to give the desired high or low impedance. In Fig. 1 the lines A, S, E lead to the antenna, transmitter and receiver respectively. The impedance transforming network across the transmitter comprises lines 9, 10, which are of a length (2n+ 1)#/4 equal to an odd number of quarter wavelengths of the transmitting frequency connected at their ends by diodes 11, 12 inanti-parallel. The line 8 between this network and line A is also of length (2n+ 1)#/4, similarly the network leading to the receiver comprises lines 2, 3 of length (2n+ 1)#/4 and diodes 5, 6. When the trans- mitter S produces an R.F. pulse the diodes 5, 6, 11, 12 conduct in the appropriate half cycles presenting low resistance at the ends of the lines. This means that the input impedance of the branches are high and little energy is lost. On receipt of a pulse by the antenna the diodes are non-conductive because the lower energy of the received pulse is below their threshold voltage. The diodes therefore present high resistance at the end of the lines. The input impedance for lines 2, 3 is low while that for lines 8, 9, 10 is high and so the received energy passes to the receiver. Single diodes in each branch may be adequate in some cases. In order to receive higher signal energies the diodes may be back biased during reception and forward biased during transmission. An alternative embodiment is shown in Figs. 2A and 2B in which oscillatory circuits with zero impedance at the transmitter frequency are used. In the receiver line coupling (2A) the diodes 21 are so connected that they short circuit the input of the receiver for transmitted signals but open the input for reception. In the transmitter line coupling (2B), however, the diodes 25 and 28 provide a signal path during transmission but break the path during reception.

The position and/or speed detector includes a data carrier (2) with at least one track (S) containing track information segments (Ai). A sensor with signal processing circuitry senses the information on the track. The track segments are made of electrically conductive, non- magnetic material and are separated by zones (Zi) of reduced electrical conductivity. The sensor arrangement inductively detects the magnetic fields (M) associated with the eddy currents generated in the track segment. The sensor includes a thin film magnetometer or gradiometer.

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.

981,447. Electron microscopes; electrostatic holding devices. PHILIPS ELECTRONIC & ASSOCIATED INDUSTRIES Ltd. Aug. 26, 1963 [Aug. 29, 1962], No. 33693/63. Headings H1D and H1P. An electron microscope is provided with an object stage in the form of a heat apertured disc 6 within an opening in which the object 8 is arranged and by means of which the object is movable in any lateral direction, together with at least one body 19 of semi-conductor material connected to the object stage 6 and arranged to contact a stationary part 11 of the microscope, the arrangement being such that, when a voltage is set up between the stationary part 11 and a conductive layer 22 on that surface of the body 19 remote from the part 11, electrostatic forces between the body 19 and the part 11 clamp the object stage 6 in such a manner as to prevent axial movement thereof. Suitable semi-conductor materials are slate, marble, agate and certain ceramic synthetic materials having a resistivity of approximately 1010 ohm-cm. In the embodiment shown an annular block 19 of agate provided with a vapour-deposited layer 22 of silver is rigidly connected in an annular groove 20 of the disc 6 with the interposition of a coating 21 of insulating material. A battery 27 and switch 28 are connected between the conductive layer 22 and the stationary part 11 by way of a lead 23 and the wall 13 of the microscope housing. Specification 824,903 is referred to.

1,116,418. Component testing. MICRO TECH MFG. Inc. April 20, 1966 [April 21, 1965], No. 17231/66. Heading G1U. A device for successively testing a number of dice formed on a semi-conductor wafer comprises a means for moving the wafer beneath a test probe so that the probe successively tests each die (e.g. for open and short circuit) and a record card which is moved beneath a punch in synchronism with the movement of the wafer. Detection of a faulty element on the wafer results in the generation of a signal which actuates the punch to record a fault in a position on the record card corresponding to the position of the element on the wafer.

1,064,646. Semi-conductor pressure transducers. SIEMENS & HALSKE A.G. Aug. 4, 1964 [July 23, 1963], No. 30698/64. Heading H1K. [Also in Divisions G1 and H4] A semi-conductor electromechanical transducer consists of a junction transistor having a pressure-transmitting needle bearing on the emitter electrode or emitter zone of the transistor whose design is such that the current density in the vicinity of the needle is greater than that in any adjacent surface region. The embodiment shown in Fig. 3 is an oxide-protected NPN silicon planar transistor having a drop-shaped emitter zone 13 formed by diffusion into the base zone 12. The aluminium emitter electrode 14 is similar in shape to the emitter region and its pointed end faces a similarly shaped base electrode 15 to provide a region of maximum current density between the electrodes. The needle is so placed that its axis intersects the line between the tips of the electrodes. Placing the point of the needle in a region of highcurrent density compensates for the loss of sensitivity arising from the use of a blunted needle to avoid damage to the semi-conductor surface. The needle is preferably made of sapphire, ruby, or boron carbide, but may possibly be made of the softer molybdenum. The pressure sensitivity of the transistor varies with its collector current. A suitable direct current bias may be applied to the unstressed transistor so that the transistor may be operated in an area of high-pressure sensitivity. To avoid the use of pressures sufficient to give non- elastic deformation of the semi-conductor this means that the transistor should be operated with the lowest standing collector current consistent with a reasonable current gain. To assist in operating the transistor in the chosen area a mechanical bias may be applied to the needle. To obtain high sensitivity the junctions should be very close to the surface of the transistor provided that they are not so close as to be damaged by the needle. This is essential only in the region of the needle and localized etching may be used so that the needle may be placed near the junction. Many uses of the transducer are suggested-an aircraft variometer is described. The Specification gives the relationship between the collector current of a conventional planar transistor with a horseshoe-shaped base electrode and the position of a needle applied at constant pressure to points across the emitter, base, and collector of the transistor.

1,088,794. Microphones. STANDARD TELEPHONES & CABLES Ltd. Dec. 17, 1965 [Dec. 23, 1964], No. 10172/67. Divided out of 1,088,793. Heading H4J. A microphone or other transducer such as described in Specification 1,088,793, comprising a semi-conductor body having at least two fixed electrodes connected thereto so that an electric current can be caused to flow in the body in a path between the electrodes, has a movable electrode spaced from the body adjacent the current path and capable of establishing a current controlling electrostatic field in the body. Vibration of the movable electrode causes a field effect modulation of the electric current.

1,213,157. Semi-conductor devices. PHILIPS ELECTRONIC & ASSOCIATED INDUSTRIES Ltd. 28 Jan., 1969 [31 Jan., 1968], No. 4581/69. Heading H1K. A transducer measures mechanical or physical parameters by their effect on the electrical resistance of a whisker of silicon carbide which forms the transducer element. This whisker is grown by recrystallization and/or condensation in a space bounded by silicon carbide in a protective gas atmosphere in the presence of lanthanum, or by the vapour-liquid-solid mechanism with iron in the liquid phase. The whisker is doped with aluminium or boron, and is provided with ohmic contacts of tungsten, or a gold alloy containing tantalum or tantalum and aluminium. Various embodiments of the transducer are described for measuring gas pressure, tensile stress, gas flow rate, temperature, electromagnetic radiation or liquid level in a container.