Abstract: A thermally responsive electric switch including two dimensionally identical, bimetallic, snap-over, part-spherical, thermally responsive actuating elements 9, 11, arranged in a nesting, contacting relationship within the end portion 7 of a housing. The first element 9 changes from a first to a second curvature when its temperature rises above a first predetermined temperature, returning to its first curvature if its temperature falls below a second, lower, predetermined temperature. The second element 11 changes from a first to a second curvature when its temperature rises above a third predetermined temperature higher than the first temperature, and thereafter remains in that curvature. A common force transmitting rod 13 bearing on the uppermost element 11 transmits the movement of both elements to a pair of contacts 3 at the other end of the housing, the contacts being in one condition when both plates have the first curvature, and otherwise being in a second condition.

Abstract: In the manufacture of a monolithic LED array, in particular a matrix array, in which portions of the array are electrically isolated from one another by channels cut or etched through the slice of n-type material, the channels are formed in two stages, relatively wide channels first being formed from the back surface of the slice to within 50 microns of the front surface, and filled with a glass frit which is bonded to the semiconductor material on each side of the channel, then narrower channels are formed from the front surface of the slice to meet the glass in the initial channels, and are similarly filled with glass frit. A glass powder suspension is introduced into each set of channels by spreading or spinning over the surface of the slice, or by electrophoretic deposition and/or capillary action, then the liquid suspension medium is removed and the glass powder is sintered.

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: 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 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: A chuteless rotary scything mulching lawn mower is described which is particularly adapted to be powered by an electric motor including sealed motors. The cutting chamber includes a toroidal portion bounded by concentric skirt walls wherein the cross sectional area of the toroid increases towards the inner skirt. The inner skirt slopes downwardly towards the axis of the cutting blade, and terminates close thereto so as to reduce air leakage from the toroid. Air passage openings are provided into the housing on the axial side of the inner skirt through which cooling air is drawn for the motor. This air stream combines with air from the toroidal chamber which is redirected by the inner skirt wall to distribute grass cuttings over a comminuting portion of the blade. The blade is sharpened to a chisel edge along the upper surface thereof, the bevelled surface of the chisel edge functioning as an air propelling surface.

Abstract: Nuclear fuel for use in nuclear reactors is provided in the form of a nuclear fuel element with an interior barrier layer interposed between the sheath and the fuel. The barrier layer incorporates particles of copper in finely divided form to provide by combination with cadmium, which is released during irradiation of the fuel, a stabilized copper-cadmium compound localized intermediate the fuel and the sheath, thus impeding attack on the sheath by the released cadmium. There is further provided a simple, low cost method for applying the barrier layer in a nuclear fuel element.

Abstract: A reservoir for an electric kettle is defined by a dome shaped shell and a planar inner bottom, which are fastened together mechanically having a room temperature vulcanized silicone rubber filler located therebetween to act as a seal. The shell is skirted by an inwardly projecting annular lip and has an inwardly projecting annular shoulder parallel with and spaced from the lip. The inner bottom is bounded by a downwardly extending annular flange, the top edge of which abuts the bead and the bottom edge of which engages the lip. The form of the kettle components permits the interior of the shell to be coated between the lip and shoulder with an annular coating of the silicone rubber whereat the inner bottom is readily snapped into position in the shell during assembly of the kettle.

Abstract: An interface apparatus, for remotely controlling a plurality of solenoid actuated switching relays having first and second energizing coils, is capable of providing momentary first and second electrical signals respectively in response to an interruption of an input signal to the apparatus and the initiation of the input signal. The interface apparatus includes a first comparator sensing a change in the input signal, a second comparator sensing a change in the output of the first comparator so as to maintain the second comparator output 180 degrees out of phase with the first comparator output, and first and second monostable multivibrators that each have a trigger input connected to the output of a corresponding comparator so as to generate a momentary electrical signal when the trigger input senses a negative excursion in a change of state at the output of the corresponding comparator.

Abstract: An electric lawn mower having a permanent magnet motor and a dynamic braking feature includes a rectifier which is assembled in a switch-box. The novel arrangement of the rectifier in the switch-box assembly is attached to an upper portion of the handle of the mower to permit use of standard three wire cord for connection between the switch-box and the motor.

Abstract: For the purpose of generating oscillations having a plurality of different frequencies, a read-only memory stores a plurality of binary words which are read cyclically. The individual pulse signals supplied by the read-only memory, each such signal representing a succession of corresponding bits read from the read-only memory, are used to control latches and the required oscillations are obtained by filtering pulse signals supplied by the latches. To guard against equipment failure, the read-only memory and latches are duplicated, the pulse signals supplied by the two sets of latches being combined by means of gates before filtering.

Abstract: A current source in which the output current from an output amplifier stage (2) is controlled by an input signal, originating in a signal source (11), to an input amplifier stage (1) incorporates, additionally to a negative feedback path from the current input path of the output stage (2) to the input amplifier (1), monitoring means (5) in the signal input path to the output amplifier (2) and control means (4) in an input path to the input amplifier (1). Monitoring means (5) monitors the current flow in the input path to the output amplifier (2) and applies, via control means (4) a signal to the input amplifier (1) such that the dependence of the current flow in the current output path on the gain of the output stage (2) is reduced. A circuit is described, as well as an application to driving a telephone subscriber line and using two current sources working in push-pull mode.

Abstract: An electrical measuring apparatus comprising a current domain magnetometer (C.D.M.) (1) and summation means (2) for summing the output pulses from the C.D.M., the sum of the summation means representing the integral of a predetermined function of the voltage and magnetic flux applied to the C.D.M. with respect to time. The predetermined function may be proportional to the product of the voltage and magnetic flux and the apparatus may produce measurements of voltage, magnetic flux, power or phase angle.

Abstract: A digital switching arrangement for use in a telecommunications exchange handling channels of digital information in time division multiplex form. The digital switching arrangement being particularly suited for use in stored program processor controller environments. The arrangement comprises a digital switching network and a control equipment. The control equipment includes an input queue and an output queue each arranged to store processor input and output messages respectively. The control arrangement is arranged to asynchronously process each output message to process switching network path connections and to generate in the input queue an input message indicative of the actions performed. Each output message includes switching network identification information indicative only of the identities of the incoming and outgoing exchange highways and channels to be involved in the switching network path to be processed.

Abstract: An arrangement for cooling electronic components mounted on a card (41) wherein the card is carried in a heat conductive frame (17) which is urged by spring bias means (25) along a guide arrangement (21) provided in an open ended structure (13) so that the frame is in good thermal contact with a cold wall (11) to which the open end of the structure is held in releasable contact to form a housing for the frame.

Abstract: In the processes of nuclear fuel manufacture, scrap material such as uncontaminated reject powder and reject pellets, which would previously have been reprocessed chemially in conversion of the uranium values by dissolution into liquid form, is now mechanically reduced by crushing in a substantially inert atmosphere and converted to a slurry having between about 70 to 85 weight per cent solids, and then attrition milled utilizing scrap sintered UO.sub.2 pellets as the reducing medium. Grinding swarf generated during the centerless grinding of UO.sub.2 pellets may also be recycled provided it is sufficiently pure.

Abstract: This invention relates to a system for protecting an amortisseur winding during the starting of a synchronous motor. The system compares the actual slip frequency of the accelerating motor with predetermined slip frequencies. These predetermined slip frequencies are each associated with a timer which measures successive time segments. Each timer is stopped when the actual slip frequency, which decreases as rotor speed increases, is less than the associated predetermined slip frequency. When the timer is stopped a successive timer is started. In this manner the acceleration of the motor is broken up into time segments. The initial timer is started when the motor starts. The final timer is stopped when the rotor field current is applied to bring the motor into synchronism. Should any timer be permitted to have its timed segment expire before being stopped, the motor is shut down. There is also provided a thermal memory which receives information from the expired timer as to its associated slip frequency.

Abstract: A remote control wiring system is provided with a transformer that supplies a low voltage signal to a low voltage sub-system. The sub-system includes a diode circuit comprising four diodes which permit energization of a first set of relays on a positive portion of a sinusoidal signal and of a second set of relays on the negative portion of the signal. A pair of triacs are provided that move the relays of both sets either in a first direction to open their higher voltage load circuits or in a second direction to close their load circuits. Previous wiring systems did not include the 4-diode circuit and were limited in capacity to control only a single gang of relays. By virtue of the improved system the capacity of the system is reliably doubled, by utilizing the whole of the low voltage control signal.

Abstract: Apparatus for connection over a telephone line to a remote data bank has provision for displaying a `page` of information received in digital form from the data bank in response to a request for that page being signalled by the apparatus to the data bank identifying the required `page`. To enable the apparatus to be connected to a particular data bank and to signal the identity of a required `page`, the apparatus has a keyboard for operation by the user. Furthermore the apparatus has an electrically-alterable memory for storing the telephone number of several remote data banks and the identity of frequently required `pages`, the information stored by this memory being accessed and utilized by operation of the keyboard on a "short-code" signalling basis.

Abstract: In the manufacture of a monolithic LED array, in particular a matrix array, in which portions of the array are electrically isolated from one another by channels cut or etched through the slice of n-type material, the channels are filled with a glass frit which is bonded to the semiconductor material on each side of the channel, to give a robust construction. A suspension of glass particles in a liquid medium is introduced into the channels, then the liquid is removed and the glass powder is sintered. The glass suspension may be introduced into the channels by spreading or spinning over the surface of the slice, or by electrophoretic deposition and/or capillary action.