Abstract: An electronic key telephone system in which three or more key telephone instruments are interconnected or connected to an exchange line, as required, by way of a central control unit, each instrument being connected to the central unit by means of two speech wires and two signalling and control wires, an adaptor unit is provided to enable connection of an external extension telephone to the central unit by way of a single pair of wires.

Abstract: The heat exchanger comprises a core of tubes engaged into tubes plates defining a peripheral groove bounded outwardly by a raised edge with a sealing gasket being placed in the bottom of the groove in order to be clamped by under side of an edge of a header box maintained by gripping means. The header box is thin walled and the edge of said header box has a top portion with a small bar interposed between said top portion and said gripping means.

Abstract: An apparatus for separating objects of a particular kind from other objects, e.g. stones etc. from potatoes during harvesting, wherein the objects fall in a stream past a detector for objects of said particular kind and, after detection of an object, a separating member positioned downstream of the detector is moved in a manner in dependence on a physical dimension of the detected object so that objects of said particular kind are directed in a first direction and other objects are directed in another direction. The physical dimension may determine a time of movement of the separating member and/or whether the separating member should be moved at all.

Abstract: A scanning arrangement for an infra-red imaging device in which a column of I.R. detectors, and similarly a column of L.E.D.'s, scans a field broadside to produce a band of parallel line scans, a number of such band scans being provided to cover the field. Each band scan is performed by a respective mirror facet of a rotating polygonal drum, the facets being tilted at slightly different angles to provide the band displacement. Non-uniformity of the column of I.R. detectors or the L.E.D.'s or the interconnecting channels tends to produce the same pattern of non-uniformity within each band. This is overcome according to the invention by periodically tilting the drum by a random fraction of a band-width so that on successive occasions a particular element of the field is processed by different detector/L.E.D. channels.

Abstract: An apparatus for expelling baseballs or other game balls with a considerable backspin. In the usual case, where the game ball is shot out generally parallel to the ground, the ball trajectory starts out relatively straight due to the rather large expulsion force, and thereupon when the expulsion force is almost spent, the backspin takes over, and the game ball will suddenly rise above the ground. This simulates a real life baseball pitcher whose fast ball has a "live hop". The apparatus features a rotating flywheel with an upper guide chute, in which is disposed a rubber pad to provide a constriction of lesser dimension than the diameter of the game ball, so that the game ball when fed onto the flywheel is passed through the guide chute, for subsequent expulsion in a generally linear, e.g. horizontal, trajectory, but with subsequent upward movement due to the backspin which is caused by the game ball passing through the constriction.

Abstract: A driving circuit for a power transistor switch in which a feedback transformer between the collector path of the power transistor and that of the driver transistor is used to provide a current drive to the power transistor that is proportional to the load current, and in which a reverse current drive, also proportional to the load current is applied by way of a third winding on the transformer to the emitter-base circuit of the power transistor to decrease the switching-off time of that transistor.

Abstract: A luggage roller featuring a diabolo-shaped wheel, which is preferably detachable from the piece of luggage, i.e. a container, to which it is mounted. The diabolo-shaped wheel is more stable than prior art configurations, because of its greater effective width leading to greater bearing area. The detachable feature of the wheel leads to changeability of the luggage roller wheel when wear occurs, so that the piece of luggage does not have to be discarded when the installed wheel wears down. This detachable feature is typically attained by providing an axle on which the wheel is mounted which is detachable from the container. The axle is generally of one of several alternative configurations in which a threaded connection is provided between portions of the axle assemblage, so that one portion of part of the axle assemblage may be unscrewed from the other portion or part.

Abstract: A double acting pinch valve with floating pinch mechanism. Two opposed rectilinear rigid members extend transversely to a flexible deformable resilient sleeve and on opposite sides of the sleeve; the flow of fluid to be controlled is through the sleeve from one end to the other. A floating piston is provided in a container, i.e. in a cylinder, which container or cylinder also has a floating mounting and suspension. The piston rod is rigidly connected to one of the rigid members, and the floating container is rigidly connected to the other rigid member. The two rigid members and the container with integral piston all have, as a feature of the invention, a floating mounting and suspension on a frame on which the sleeve is mounted, so that these elements are freely displaceable relative to the frame and towards or away from the sleeve.

Abstract: A time relay comprising a device (1) arranged to produce an output (F) having a frequency representative of a parameter (I) to be monitored, a comparator (5) responsive to the output (F) for producing an output (IN) when the value of the monitored parameter exceeds a setting value, and relay operating circuitry for operating the relay when the comparator produces an output for a time determined by the relay characteristic for the value of the monitored parameter. The device is suitably a Carrier Domain Magnetometer (C.D.M.) and the operating circuitry suitably includes a digitally addressable memory (8) in which the relay characteristic is stored.

Abstract: An improved ammoniacal alkaline etchant solution and method of reducing etchant undercut for use in etching copper and copper-containing alloy traces on substrates having resist-coated areas and non-coated areas, which reduces the amount of undercutting beneath the resist-coated areas that lie above the copper traces. The improved etchant solution contains an organic undercut inhibitor which can be either 5-nitro-1H indazole or pyrazole and the improved method includes the step of incorporating said organic undercut inhibitor in a standard ammoniacal alkaline cupric etchant solution. The organic undercut inhibitor causes the formation of a bath-insoluble, physically weak, etch-resistant film on the copper substrate. Said film serves to protect the side walls of an etched depression and thereby diminishes undercutting.

Abstract: An arrangement for establishing a mechanical connection between two relatively movable structures, such as a fixed or floating marine structure and a vessel for facilitating the transfer of things between them has a double boom assembly carried by a support rotatably mounted on one said structure for enabling the boom assembly to be slewed about a generally vertical axis, the double boom assembly comprising a main boom pivotal on the support so that it can be raised or lowered, and an auxiliary boom pivotal on a trolley movable along the main boom, and, coupling means connecting the outer end of the auxiliary boom to co-operating means of a second structure, and including a universal joint which permits movement between the second structure and the boom assembly.

Abstract: A 360.degree. open circular refrigerated display case which features a plurality of horizontal circular display shelves, aligned in a vertical series one above the other. Unique cold and warmed air circulation patterns are provided by the configurations of the shelves and central foraminous ducts. Cascading air curtains flow from top to bottom in the refrigerated display case in a unique flow pattern, i.e. downwards from shelf to shelf and successively inwards and outwards below each shelf, guided by the shelf itself which acts as a baffle. A specific circular configuration of a refrigerated display case with horizontal trays and cold air flow about the trays, which are hollow, as well as a specific arrangement of two adjacent trays or a single hollow tray, as well as the baffles and flow arrangement, as disclosed.

Abstract: A synchronization arrangement for delaying excitation of the field winding (5) of a brushless synchronous motor until the motor rotor has run up approximately to synchronous speed in which the appropriate moment for applying the field excitation is determined by monitoring two signals respectively representative of the currents in two rectifying devices (11, 15) separately connected, oppositely poled, across the motor field winding.

Abstract: A turbine or like rotary machine of the kind in which a fluid, either a liquid or gas, is arranged to act on a plurality of generally radially extending rotor blades, has each rotor blade fixed in position relative to the rotor hub and is substantially symmetrical about a plane perpendicular to the rotor axis, the blades having surfaces which are of generally aerofoil shape and being mounted with their leading edges facing in the same circumferential direction. The rotor of such a turbine can be driven by a generally axial flow of fluid, the direction of rotation being unchanged when the direction of flow of the fluid is reversed, so that it can be used to advantage in an oscillating or periodically reversing fluid flow. Such a flow may be provided or produced for example, by naturally occurring movement of air or water.

Abstract: In apparatus for the manufacture of mineral insulated cable by a continuous process in which the tubular sheath is formed by bending and seam welding travelling metal strip, and insulating powder is fed through a powder delivery tube into the sheath while the latter is travelling vertically downwards, the conductor wires are introduced into the sheath down the outside of the powder delivery tube through guide means which may include, for a wire adjacent to the seam, a tube having an aperture in its wall adjacent to the weld area. Excess heat is removed from the weld area by either a wire or an air gap adjacent to the weld. When the sheath is formed of an oxidizable metal such as copper, means are provided for delivering a continuous stream of rare gas to the underside of the weld area. Various configurations of the powder/wire delivery system are described.

Abstract: An antenna system has a parabolic reflector mounted so that it points generally downwards and a primary aerial is located at the focus of that reflector. Waves from the primary aerial are reflected back by the parabolic reflector to a reflector plate through an aperture in which the primary aerial projects. Scanning in both elevation and azimuth is effected by movement of the reflector plate.

Abstract: An alkaline copper etching working bath for dissolving copper containing an etch accelerating additive selected from the group consisting of cyanamide and its precursors. The accelerating additives when added to the alkaline copper etching bath increase the etch rate and reduce undercut. The bath includes cupric ions, an ammonium salt such as a chloride and/or a carbonate, ammonium hydroxide to achieve a pH greater than 7, water, and the etch accelerating additive. The invention includes etching baths, methods for their use, the preparation of a certain etch accelerating additive and the provision of certain cyanamide precursors.