A syncrhonization arrangement is disclosed for synchronizing a receiver with a transmitter whose frequency is hopping through a sequence of predetermined frequencies arranged pseudo-randomly. The transmitter includes a time base circuit in the form of a string of dividers operated from a stable oscillator. One divider produces (in this example) a 28 bit synchronization signal which changes state once every sixty four hop frequencies. The 28 bits control a keystream generator which produces a pse...

A receptacle for holding water and other nutrients a portion of which is adapted to be placed below grade for irrigating plants, and includes apertures in the bottom of the receptacle to allow the slow migration of liquids outwardly therefrom and a lid on a top face suitably formed to prevent evaporation, the apertures provided with a semispherical cap to prevent fouling.

A window construction incorporates a pane or panes of glass retained in a frame by glazing beads inserted between the glass and the frame at the outside of the window and incorporates means for preventing disengagement of the glazing beads other than by breaking the glass. The glazing beads may incorporate oppositely acting retaining formations engageable with at least one co-operating retaining member on the frame, each retaining formation being arranged to be more firmly engaged by movement of...

A navigation system provides a shore-based continuous visual signal to a ship navigating a channel or approaching a jetty. This indicates to the ship the optimum velocity program that it should be following, which is normally a gradual reduction of speed as the ship approaches its destination. The signal is a moire fringe display (33, 34, 35) from a rotating projector (21) which tracks the intended path under the control of a computer program. From the ship, the fringes are static if it is at th...

Storage apparatus for combustible or explosive material, the apparatus comprising a substantially closed, heat-resistant container, an opening in a wall of the container to enable flow of quenching fluid into the container from an external supply of said quenching fluid, a valve which normally prevents flow of said quenching fluid into the container through the opening and detector means responsive to penetration of a wall of the container by a projectile or fragment and which, in the event of s...

In pressure sensor systems based upon a micromachined silicon pressure sensor comprising a resonantly vibratable beam supported on a diaphragm, the beam is excited into resonant vibration by directing an optical excitation signal at the beam resonant frequency, via an optical fibre 26, onto a part of the sensor other than the beam, preferably the diaphragm. To detect the vibrations, the underside of the beam 16 and the adjacent upper surface of the diaphragm 18 are together arranged to define a ...

A stabilization system for a towed aerodynamic body 1. The body is provided with two, contra-rotating tubular shrouds 3, 4 each fitted with a set of vanes 5, 6. When the towed body is disturbed by the towing aircraft's wake, the gyroscopic inertia caused by rotation of the shrouds exerts a damping effect on the subsequent oscillatory motion of the towed body. In one embodiment, the shrouds are coupled by wheels which constrain the shrouds to rotate in opposite senses. Hence gyroscopic precession...

A lens system is provided which includes two lens units. The first lens unit includes two meniscus lenses whose concave surfaces face each other and the second lens unit has a positive power. The system can be configured to have a wide field of view and/or to be telecentric. In its basic form, a well-corrected lens having a relatively large aperture and field of view is achieved through the use of only three lens elements.

A device is employed in a recoil system for large-caliber ordnance, to effectuate damping of the recoil system during its rearward movement with simultaneous storage of energy obtained from the recoil kinetic energy of the recoil system. The device then supplies thus stored energy, to the recoil system on its recuperative movement which follows the recoil movement. The device may also supply energy to other energy consumers disposed on or in the proximity of the gun. The device may also receive ...

A helmet system comprising a helmet (11), a vizor (13) pivotally mounted on the helmet, and mounted on the vizor (13), an electro-optical system, e.g. a night vision goggle, including an eyepiece (33) positioned between a transparent part (19) of the vizor and the user's eye so as to provide the user with a view of a scene forward of the user through the eyepiece, the eyepiece also serving as a combiner to provide the user with a virtual image of a display produced by the electro-optical system ...