Smiths Industries Plc

Smiths Industries Public Limited Company

David J Vallins

James C Green

Christopher M Thomas

David V Stephens

An electrical assembly including a digital logic circuit, an analogue processing circuit and an analogue power circuit is connected to test equipment. Test data from the equipment is supplied to the circuits via a shift register divided into three serial portions. One portion is connected between the digital circuit and the processing circuit, another portion is connected between the processing circuit and the power circuit, the final portion being connected at the output of the power circuit. The portions can isolate the circuits from each other and supply test data to the circuit under test. The test data output from the circuit is clocked along the register to its output.

Shift register connection between electrical circuits

In a cathode-ray tube display system, signals defining the coordinates of the element of the screen on which the cathode-ray beam is incident in its raster scan are supplied to a comparator together with signals defining the coordinates of a series of points defining the image to be displayed. The comparator derives a brightness-weighting signal in respect of each element in accordance with the proximity of that element to those of the points defining the image within a predetermined proximity. The predetermined proximity may be equal to the separation between the points. The system also includes a store, brightness-weighting signals being added together in the store to produce a total signal for each element that is used to control bright-up of the element. The store may include two units that each receive the brightness-weighting signals in respect of elements in two regions comprising several raster lines each, signals from one region being read out of one unit while signals from the other region are written into the other unit. Alternatively, the store may include a plurality of units associated with respective regions of the screen, the units being written into and associated with a particular region only if brightness-weighting signals indicate the presence of a part at least of the image in that region. The system may also include a delay unit that receives first brightness-weighting signals in respect of odd numbered elements along the raster lines and a processor that interpolates from the first signals second signals in respect of the even numbered elements, the second signals being output intermediate the first signals.

Display systems

A head-up display involving display of pitch-bar symbols in the line of sight of an aircraft pilot is generated using raster scanning of a cathode-ray-tube screen and bright-up in accordance with stored information relating to the wings-level or other datum attitude of the aircraft. Variation of the pitch-bar mapping in the display area to follow change of attitude of the aircraft is made through transformation in accordance with pitch and bank angles applied to the point-by-point progression of the raster scan, and the visual staircase effect of symbols inclined to the line-scan is reduced by controlled variation in brightness from point to point. Each point (x.sub.d, y.sub.d) in the progression of the scan through the display area is mapped back incrementally into the corresponding point (x.sub.p, y.sub.p) of the stored datum-attitude map, through a transformation in rotation dependent on the bank angle .phi.. Computation of x.sub.p involves summation of discrete signals representative of x.sub.d cos.phi. and y.sub.d sin.phi., and of y.sub.p involves summation of discrete signals representative of -x.sub.d sin.phi. and y.sub.d cos.phi.. The eight most-significant bits of the eleven-bit computed values of x.sub.p and y.sub.p are used to read out four bits stored in respect of the point (x.sub.p, y.sub.p) to define the brightness of that point and three immediately-adjoining points in the datum-attitude mapping. Brightness-weightings applied to the four digits respectively are derived from read-only memories in accordance with the three least-significant bits of the computed values of x.sub.p and y.sub.p, and the four bits so weighted are added together to provide the bright-up video input to the cathode-ray tube for the point (x.sub.y, y.sub.d).

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Cheltenham, United Kingdom

David J Vallins