Abstract: A surface-discharge igniter having concentric electrodes includes a gap at its operative tip which separates one of the electrodes from the exposed semiconductive surface of a semiconductive pellet that is interposed concentrically with the two electrodes. The said one electrode, which may be either the inner or outer electrode, is connected electrically to the pellet at the bottom of the gap away from the operative tip, whereas the other electrode makes contact with the pellet at, and in the region of, the exposed surface but is otherwise insulated electrically from it. Where the gap separates the inner electrode from the semiconductive surface then the outer electrode may be flared inwardly to establish its electrical connection with that surface. On the other hand, where the gap separates the outer electrode from the semiconductive surface the inner electrode may be flared outwardly, or provided with a cap that extends outwardly across the surface, to establish the connection with it.

Abstract: Liquid-measuring apparatus for measuring the drainage of urine from a patient comprises a measuring cylinder and a bag which is of substantially larger capacity than the cylinder and is situated beneath the cylinder. Tubing extends downwardly to the bag from within a compartment of the cylinder, the compartment being formed by an additional tube which is closed at its upper end and perforated near its lower end. The cylinder is vented to ambient atmospheric pressure above the level of the upper end of the tubing connected to the bag. Every time urine collected in the cylinder reaches this level, an automatic siphon action drains a predetermined quantity of the urine from the cylinder, through the compartment and the tubing, into the bag. The total quantity of urine drained from the patient can be measured at any time by means of a coarse reading taken from the bag and a fine reading taken from the cylinder.

Abstract: A moving-coil electrical instrument in which an electric coil mounted for angular displacement about an axis embraces an annular core which is disposed between radially-spaced walls of a housing to define two radially-spaced, annular air-gaps through which extend the inner and outer limbs respectively of the coil. The inner air-gap is made shorter (in the direction of the lines of magnetic flux) than the outer air-gap, so that any change in the force induced into the outer limb of the coil, arising from, for example, radial misplacement of the core, is accompanied by a greater change in the force induced into the inner limb. Thus the difference in the radial distances from the axis of the inner and outer limbs is offset, and the changes in the torques induced into the inner and outer limbs balance one another. Alternatively, or additionally, the inner air-gap may be made wider (measured parallel to the respective limb of the coil) than the outer air-gap.

Abstract: In a head-up display system video signals derived by a television (or infra-red) camera which is mounted on the aircraft nose to view substantially the same scene as viewed by the pilot along his line-of-sight through the partially-transparent reflector of the head-up display system, are mixed with the video signals which are supplied by a waveform generator in accordance with aircraft-attitude and weapon-aiming symbology that is used for projection onto the reflector. The combined signals, representing the external scene with the symbology superimposed, are supplied to a video-tape recorder for subsequent, or immediate, replay by a television monitor in the aircraft or via the pilot's head-up display unit, and are also supplied to a transmitter to enable recording and display to be carried out at a ground station.

Abstract: An altimeter has a rotatably-mounted index that is driven to rotate through one complete revolution around a scale for each change of 1,000 feet in altitude sensed by two evacuated manometric capsules the number of revolutions of the index is indicated by numerical markings visible through an arcuate window which breaks into the scale against a `zero` arrowhead at the top-center of the scale. The markings are distributed around the opaque circumferential-margin of a transparent disc that is mounted coaxially with the index and is driven in the counter direction to the index through step-down gearing. Successive ones of the numerical markings are rotated to the zero arrowhead to indicate the number of units of 1,000 feet appropriate to the altitude measurement, upon successive revolutions of the index.