Smiths Industries Plc

Harry Gibson

John W Jones

Edward S Eccles

Peter F Maycock

An electrical indicator for providing a digital display representation of the value of an input variable has four display areas, each area being arranged to display an individual one of the digits of a four digit number representative of the value of the input variable. Each display area is in the form of a matrix array of light-emitting diodes. The indicator includes a computing unit which is arranged to energize those diodes making up each digit and, by varying the energization, to cause displacement of the least-significant digit within its display area upon change in value of the input variable. Digits within the other areas remain stationary until an adjacent less-significant digit is moved between `0` and `9` when the more-significant digit is displaced in synchronism with the less-significant digit. The computing unit includes a store which contains information as to which diodes should be energized to represent any particular digit. The computing unit initially addresses only those locations in the store relating to diodes along one row of the matrix, and is incremented subsequently to read out information relating to other rows.

Electrical digital display indicators

An electrical indicator has a consecutive series of light-emitting diodes which are arranged along a straight or curved reference scale. A limited region of the series, comprising several diodes, is energized and this illuminated region is displaced along the scale upon change in an electrical input variable supplied to the indicator such that the position of the region provides an analogue indication of the value of the input variable. To improve the appearance of the display and reduce power consumption, the brightness of the region varies along its length with one or both of the outermost diodes being energized at lower levels than another of the diodes. The indicator may include a shift register having a number of storage locations, each for storing signals representative of a corresponding one of the light-emitting diodes, the signals at these locations being displaced in accordance with change in value of the input variable. Signals output from each storage location of the shift register are supplied to a gate which controls switching of a transistor that is connected in series with a resistor in the energizing circuit of each light-emitting diode. Each energizing circuit includes two such transistors and associated gates which control the degree of brightening of each light-emitting diode by switching one or more resistors in parallel in the circuit. The gates are connected to control brightening of one diode in accordance with brightening of one or more other diodes.

Analogue electrical indicators having a series of

An aircraft-speed indicating instrument has an index which is movable against a scale to provide a reading of airspeed, and a digital indicator which is selectively operable to provide a digital reading of either Mach number or the airspeed. The index and the digital indicator are driven by respective control systems supplied with a multiplexed electrical signal containing information representative of both Mach number and airspeed. Each control system includes gating means which is operable to pass only those parts of the multiplexed signal necessary for the associated control means to provde the desired reading.

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Bredon, United Kingdom

Harry Gibson