Improvements relating to radar display systems

... 877,159. Radar. ASSOCIATED ELECTRICAL INDUSTRIES Ltd. Dec. 1, 1959 [Oct. 15, 1958], No. 32935/58. Class 40(7) In a ship-borne radar with a true motion PP and CRT display, when the spot representing the position of the ship crosses a selectable one of four imaginary threshold lines AB, CD, EF and GH, Fig. 1, defining a square symmetrical with respect to the screen, the spot is automatically reset to a diametrically opposite position, outside the square, the selected threshold line being selected automatically and continuously in accordance with the instantaneous heading # of the ship. As described the north threshold line AB is selected if the ship's heading is within the sector bounded by the directions NW and NE and the other threshold lines are selected in a corresponding manner. As shown in Fig. 2 the ship spot is displaced in accordance with the movement of the ship by applying shift voltages V N and V E to orthogonal shift coils 6 and 7. A sine-cosine potentiometer 1 set in accordance ...