Abstract: A data receiver is required to detect successive 50-bit frames of data which are transmitted without any pause between frames and with a start bit value of 1 as the only start-of-frame indication. Error detection and correction is obtained by appending at the transmitter a 13-bit check word to 36 data bits (and the start bit), the value of the check word being chosen such that division of the error-free composite 49-bit code word by a predefined generator polynomial yields a syndrome (remainder) of zero. Calculation of a new syndrome value by the receiver at the speed necessary during initial frame synchronization (i.e. for each successive bit) is effected with an iterative procedure in which the previous syndrome value is left-shifted one place and the newly received digit is appended to it; the generator polynomial is added to the result by modulo-2 arithmetic if the most significant digit of the shifted syndrome word is a 1; and the remainder of -2.sup.

Abstract: A fluid density transducer with a vibrating tube 16 coupled to excitation pick-up transducers 32 utilizes an elliptical tube 16, having a small degree of ellipticity, to compensate for the variation in the natural frequency of vibration, resulting from a variation in the fluid pressure, i.e. a rise in fluid pressure tending to lower the frequency produces a more circular and hence stiffer tube cross-section tending to increase the frequency. A sealed evacuated chamber 36, formed by connecting together cylindrical nodal masses 24 and 26 using a flexible coupling 28, is used to enclose the vibrating tube 16, thus avoiding the risk of contaminating, and thereby also affecting the calibration of, the tube 16. The tube is supported at each end by a spring plate 12 fixed around its outer periphery to a collar 10 and around its inner periphery to an end-plate 25 of the nodal mass 24 or 26.

Abstract: In order to allow a wide range of instruments to be assembled from standard modules, there is provided a range of different diameter housings with their glasses spun in and sealed by an O-ring. A housing can be trimmed to length as required. Different types of panel mountings can be fixed over the front rim of the housing. One of a range of standard movements is mounted between plates and matched to the housing diameter and retained therein by releasable catches. The catches may be turnbuttons cooperating with pegs projecting inside the housing. Alternatively, leaf spring catches slidable radially outwardly on the plate can engage in an annular groove inside the housing and be locked in position by clamp screws. The rear end of the housing is plugged by an O-ring sealed base which carries either a terminal part/connector structure only or also a range scaling circuit enabling the same movement to handle different input signal ranges. The pointer on an offset arm sweeps over a scale which can be hub lit.

Abstract: A capacitor header having the mechanical characteristics of a modulus of elasticity in the range from 50,000 to 200,000 psi and a tensile strength in the range from 3,500 to 80,000 psi has pressure formed therein on the aluminum terminal of which portions thereof have been increased in the range of 0.002 to 0.020 inch larger than the holes provided in the header.

Abstract: In order to compensate the hydrodynamic pressure on the turbine of a flowmeter, means are provided to create a zone of reduced pressure of constant value upstream of the turbine hub, together with means for creating a zone of pressure, on the downstream face of the hub, varying in a defined manner as a function of the axial position of the turbine. The pressure difference thus created on either side of the turbine hub produces a reaction force tending continuously to balance the hydrodynamic pressure of the fluid whatever the flow rate. The invention is particularly applicable to high flow rate water meters.

Abstract: A microprocessor-based torque measuring system for a twin engine-aircraft gas turbine engine installation comprises respective inductive sensors 12,14, one for each engine. The sensors are positioned to co-operate with respective pairs of toothed wheels, which are secured to axially spaced points on the engine shaft whose torque is to be sensed and have interlaced teeth whose spacing circumferentially of the wheels varies with torque. Each sensor produces a torque signal which, after suitable shaping, has a mark-space ratio representative of torque, and the respective durations of the mark and space periods of the signal are measured digitally by counting clock pulses during successive groups of mark periods and space periods. The accumulated counts are then subjected to recursive digital filtering by the microprocessor, in accordance with a predetermined function approximating the response of a second order Butterworth filter.

Abstract: A probe for sensing direction of flow of an injected current pulse along a conductor of a circuit under test is linked to an ATE, to be triggered to inject the pulse during a test sequence at a step previously found by the ATE to establish a faulty state in the circuit. Thus, the faulty one of several components connected to a circuit node can be identified. The probe itself can also be used independently, and injects an approximately triangular-waveform current pulse which has a steep rising edge and a less steep falling edge, thereby inducing a voltage pulse which is asymmetric about the zero voltage level and thus permits discrimination of the direction of current flow. The probe may have a single current injection contact disposed between the limbs of a bifurcated core for the pick-up coil.

Abstract: An improved viscous dampening arrangement for a taut-band suspension system in an electrical indicating instrument includes a hub associated with the stator and a turret associated with the rotor. The hub and turret each have central openings for receiving the taut-band. The hub and turret are arranged, in use, in a spaced-apart facing relationship with the facing portions of hub and turret being tapered in a controlled fashion. A viscous dampening fluid is provided between the hub and turret and an anti-wetting agent is applied to the surfaces of the hub and turret where the dampening fluid is not desired. The geometry of the tapers is chosen so as to minimize the effects of longitudinal and radial shocks and vibrations on the electrical indicating instrument.

Abstract: A digital circuit tester for performing signature analysis is provided with a memory (32) for storing successive samples at 256-bit intervals of the progressively evolving CRC signature of a signal in the circuit under test. Comparison with the same sequence from a known good unit facilitates identification of faults, even in feedback loops. To identify the first failing bit, the test is repeated, but with the CRC feedback connections disabled, and successive blocks of the actual data stream are stored, beginning at the point corresponding to the first faulty signature sample, for subsequent inspection and comparison with the data stream from the known good unit.

Abstract: System and apparatus for treating data derived in serial pulse fashion from a source such as a meter. Data words are recorded upon a magnetic bubble memory which is portable and which includes real time and identification data in addition to pulse source data. The portable storage device incorporating the magnetic bubble memory is inserted into reader apparatus for transmission by telecommunication to a translator station which may be located remotely from the reader station. Cyclical redundancy check verification of the transmission is made between the stations to assure proper transmission. Further, the translation station carries out data verification checks. Erase apparatus is provided in the vicinity of the reader apparatus to carry out a memory check for the magnetic bubble memory and an erasure thereof through the insertion of zeroes therewithin.

Abstract: A modular backlighted analog/digital display for use in a cylindrical aircraft instrument housing. The analog indicator dial is backlighted by an illumination source diffused by a translucent light collecting plate having a configuration corresponding to that of the analog dial. A polarizing filter is mounted in an opening formed in a portion of the light collecting plate to enhance image contrast of the digits of a digital display of the self-illuminated type, e.g. an incandescent or LED digital readout, that is exposed through a cutout portion formed in the analog dial. In addition, the interior of the opening in which the display is received can be coated with a light opaque material to prevent light scattered from the light collecting plate from reaching the face of the digital display and washing out the digits. The analog pointer is formed from a translucent material and is connected to an analog meter mechanism.

Abstract: A tape entrainment device especially for a magnetic recorder, comprising a roller (11) tangential to the periphery of each of the reels (9 and 10) and an endless belt (12) which passes between the roller and the reels and engages an arc of the periphery of each of the latter.The roller, which entrains the tape by friction by means of the belt on which it bears, is integral in rotation with an element (24 and/or 26) which is entrained on the one hand in rotation about its own axis and on the other hand is forced mechanically to move relative to the support along a circular path as close as possible to the path of the roller.

Abstract: Electrical contact between foil electrodes and conductive coated plates in a solid dielectric capacitor is improved by coating or embossing the foil electrodes with a conductive particulate material.

Abstract: A receiver, for receiving a signal comprising a carrier signal modulated with a digital signal, comprises a circuit for demodulating the received signal to produce an output signal which contains the digital signal. Because of repeated filtering, the digital signal is typically in the form of an approximately sinusoidal signal, which has a component whose frequency is equal to half the basic bit rate of the digital signal: because of noise, this component is subject to considerable timing jitter. To overcome this, the output signal is digitized and applied to a digital correlator, where it is correlated with a reference signal whose frequency is also equal to half the basic bit rate of the digital signal. The reference signal is preferably derived from a phase-locked loop locked to the carrier frequency.

Abstract: Digital simulation apparatus, e.g. a digital coastline generator, for simulating a terrain-representative display of the kind produced by a movable scanning-type display device, e.g. a radar display device, comprises a main store for storing digital data representative, in Cartesian co-ordinate form, of terrain features such as contours and buildings in an area, known as the playing area, typically 256 nautical miles by 256 nautical miles. The data is divided into groups relating to contiguous zones each typically 2 nautical miles by 2 nautical miles. The apparatus further comprises means for producing a signal representative of the current position of the display device in the playing area, means for producing successive signals representative of successive segments of scan of the display device, and means responsive to these signals to select from the main store those groups of data corresponding to zones intersected by the current scan segment.

Abstract: An electricity meter for metering the amount of electrical energy supplied by a power supplier to a power consumer is provided with fraud detection means for detecting the presence of an external shunt which has been connected to by-pass its internal current sensing means. The detection means, which comprises a differential current sensor for sensing the difference between the respective currents flowing to and from the consumer via the meter and a multiplier for multiplying this current difference by a signal derived from the supply voltage, is arranged to operate a circuit breaker, and/or to compensate the energy measurement of the meter, and/or to provide a warning to the supplier. The differential current sensor also senses when current is being taken between the live wire and earth on the consumer's side of the meter.

Abstract: A transmission system, for transmitting signals over an electrical power distribution circuit, comprises a transmitter arranged to produce at least two carrier signals of different frequency and to modulate each of them with the same digital signal. The respective frequencies of the carrier signals are derived by frequency division from a common master oscillator, and are thus phase-coherent. The system includes a receiver for receiving the signals, comprising a respective input circuit for each modulated carrier, the input circuits each being tuned to the frequency of their respective carrier signal. A plurality of oscillator signals of different frequencies, derived from a variable frequency oscillator, are used to beat the received carrier signals to respective signals at a common frequency, which signals are summed.

Abstract: A device for measuring a quantity such as the electric power in a polyphase alternating current network including at least two phase conductors and a reference conductor, of the type comprising two measuring devices which are associated respectively with the two phases and the outputs from which are connected to a summation device.A supply circuit connected to one of the phases is associated with the corresponding measuring device, and a device connected to the other phase ensures the supply to the other measuring device and to the summation device, the supply circuit and the supply device being connected through a high-impedance tie circuit, the summation device being supplied if at least one of the phases is under voltage with respect to the reference conductor.

Abstract: A radio-controlled device for use in a power distribution circuit, typically for tariff-switching, load-shedding or off-peak load-switching purposes, includes a radio receiver having an aerial circuit which includes a ferrite annulus. The device is typically mounted in an electricity meter connected in the power distribution circuit, with the ferrite annulus surrounding one or more wires of the distribution circuit down-circuit of the meter. The wire or wires surrounded by the ferrite annulus, which typically extend all over the house or other building in which the meter and the device are installed, therefore serve as an aerial for the radio receiver in the device, thus alleviating the problems which can arise when the device is mounted in a location where radio reception is poor.

Abstract: A modular analog/digital display for use in a cylindrical aircraft instrument housing is designed to enable the digital components to be assembled without interference to the analog meter mechanism. The digital display is of the leadless type and is clamped under compression to a circular circuit board with a pair of contact strips in registration with contacts formed on the circuit board and digital display. The design also features a screw-on dial pointer which facilitates the assembly of the digital display components and dial to the analog meter mechanism without interference.