Patent GB-885649-A (GB)
Title: Improvements in or relating to apparatus for air traffic control
Inventor: PARKER ERIC
IPC: G01S1/02
Filed: 1958-09-05
Abstract: 885,649. Pulse radar. DECCA RECORD CO. Ltd. Sept. 4, 1959 [Sept. 5, 1958], No. 28661/58. Class 40(7). Air traffic control apparatus comprises a cathode-ray tube (C.R.T.) providing a twodimensional display, means generating a number of marker signals each of which is applicable to the C.R.T. to produce a trace which is gradually displaced along a predetermined track across the face of the C.R.T. according to a predetermined speed pattern, the various markers being arranged to follow one another along the same track in a regular repetitive sequence at predetermined intervals and switch means operative to select a particular marker signal and to apply it to the C.R.T. The embodiment described relates to markers produced in the inter-scan periods of an airport pulse radar employing a plan-position indicator display (P.P.I) 10 with fixed deflector coils fed according to the system disclosed in Specification 818,477. Each controller is provided with such an indicator and controls aircraft flying along a particular route. The markers are generated by x and y potentiometers 30, 31 each of which incorporates taps 32. .35 and motor-driven wipers 36 evenly spaced about the driving axis 37. Potentials are applied to the taps to define points K, L, M and N respectively of an approach route KLMN and the wiper spacings are such as to provide for successive deliniations of such route on the P.P.I. at intervals of, say, two minutes; the taps are positioned along the potentiometer tracks by amounts corresponding to the time required for aircraft to fly between corresponding points along the route. Additional pairs of potentiometers are employed to cater for wind speed on each section of the route by corresponding adjustment of the positions of taps 32. .35, and the programmed speeds set into thepotentiometers are calibrated by a speed-indicating voltmeter e.g. 42. The wiper voltage outputs are fed to ganged selector switches 45, 46 and thence, under the controller's selection, to electronic switch 21 for interscan marking. The marker outline is formed as a circle or ellipse by phase-quadrature modulator 49 fed from A.C. source 50. The supervisor of the controllers is provided with flight data by cathode-ray tubes 66 forming part of a data transmission link 65 as described in Specification 822,769, and he allocates landing times to the controllers by switches 67, a particular allocation being notified to a controller by concurrent operation of a switch to change the marker into a straight line by insertion of in-phase modulation by modulator 49; the relative amplitudes of the in-phase components is controlled by a knob 71 coupled via a 2:1 gear-box to a dial 74 so that directions can be given to a radar-indicated aircraft to bring it on to the desired track or to cause it to zig-zag so as to lose time. This marker may also be used to check whether collision courses occur. An automatic computer for deriving heading information for aircraft to follow to bring it on to the desired course may be provided, the computer inputs being taken from an auto-following unit 80 connected to the radar receiver and from lines 47, 48. An audible or visual alarm may be given when an aircraft diverges by more than a predetermined amount from the programmed route.