1,056,820. Radar. BOFORS A.B. Dec. 31, 1964 [Jan. 15, 1964], No. 53046/64. Heading H4D. [Also in Division G4] In a system for intercepting and attacking aerial targets and including a searching and detecting apparatus SR, Fig. 1 (not shown), affording target slant range Al 0 and azimuth sv 0 therefrom and a director ER, a distance P from SR, incorporating a sight rotatable in azimuth and elevation and including range-measuring means, the director sight is caused to scan the vertical circular arc C corresponding to the target range and azimuth from SR by automatically computing from quantities sv 0 , Al 0 , P and a quantity hv 0 representing an arbitrary angle of elevation from SR and varied over a predetermined range of values, the quantities sv 1 , representing azimuth, and hv 1 representing elevation (angular), of the corresponding point from ER. In the embodiment SR and ER are radars the latter producing a signal e sf representing the difference between target azimuth and the azimuthal direction sv<SP>1</SP> 1 of the aerial 5, a signal e hf representing the difference between target elevation and the elevational direction hv<SP>1</SP> 1 of aerial 5, and a signal e af representing the difference between target slant range and that afforded by the range measuring unit in the radar, these signals actuating appropriate servomotors to reduce the signals to zero. The setting of quantities Al 0 , sv 0 into the analogue computer R at SR is performed manually or automatically via a telemetric transmission from ER, the quantity P is set manually and the quantity hv 0 is varied manually or automatically over the range 0 degrees to 90 degrees; the radar ER thereby scans arc C until it detects the target M and then tracks it automatically by known means. It is demonstrated, Fig. 2 (not shown), that if the radar is to be laid on a point Q on arc C the following equations (5), (8), (9) must be solved: where x 1 , y 1 are co-ordinates of point Q in a Cartesian co-ordinate system centred on ER, x p , y p being co-ordinates of ER in a Cartesian co-ordinate system centred on the search radar SR where z 1 is the third co-ordinate of point Q in the system centred on ER, and equals Al 0 sin hv 0 - z p Ah 1 = horizontal range of Q from ER = x 1 cos sv 1 + y 1 sin sv 1 . . . . . (6), Al 1 = slant range of Q from ER = Ah 1 cos hv 1 + z 1 sin hv 1 . . . . . (9) The corresponding computer configuration is shown in Fig. 3 all signals being A.C. a signal derived from potentiometer P4 and resolvers R1, R2 is added in A3 with a signal from a potentiometer P1 to yield x 1 , adder A2 yields y 1 and adder A1 yields z 1 . Resolver R3 provides a signal e sa corresponding to the L.H.S. of equation (5) for aerial azimuth control by servomotor SS until e sa is reduced to zero. Resolver R4 provides a signal e ha corresponding to the L.H.S. of equation (8) for aerial elevation control by servomotor SH until e ha is reduced to zero. A potentiometer P5 affords an output corresponding to the range Al<SP>1</SP> 1 from radar ER as provided by a servomotor SA, and a difference-circuit D yields an error signal e aa to make Al<SP>1</SP> 1 = Al 1 . Thus radar ER scans along arc C as hv 0 is varied, until it finds target M whence switches V1, V2, V3 are changed-over for automatic tracking. The computer may be modified by multiplying the input reference voltage 8 by a factor 1/Al 1 ; this is stated to enable higher computing accuracy to be achieved. In order to permit correct operation when the aerial of radar ER points directly opposite to that on the arc at which scanning is to be started a phase-sensitive device FD and a relay R are provided. For movable fire control radars, axes related to those of the vehicle are necessary; a set of resolvers, Fig. 4 (not shown), are then inserted between a-a and b-b in Fig. 3a (not shown) for co-ordinate transformation.