546,664. Searchlight control systems. SPERRY GYROSCOPE CO., Ltd., NISBET, R. H., and WALTERS, D. G. Oct. 10, 1940, No. 15129. [Class 40 (i)] In a system comprising a number of searchlights individually mounted for rotation in azimuth and elevation under separate control in response to data transmitted from a common control station, the control is effected so that the individual beams move in unison but with relative angular displacement whereby they are caused to move as a composite beam. Basic angular settings are determined at the control station, the relative angular displacements being included in the transmitted data or effected at the individual searchlights. The beams may be fanned in azimuth or elevation or the composite beam may be conical. Arrangements are provided for scanning, for changing the form of the composite beam, and for compensating reduction of azimuthal spread with increase of elevation. In the system shown in Fig. 1, to which the invention is applied as shown in Figs. 2 and 3 and which comprises only azimuth control, the similar elevation control being omitted, the sound detector 1 and one searchlight 3 are interconnected by a selsyn system 7, 9, 10 supplied from mains 8. When the rotors are not in correspondence, the rotor of 10 provides an output to a phase detector 11 which may be as described in Specification 523,539 and which provides an indication at 12 of the direction of searchlight movement required to restore correspondence. This movement is controlled by handle 4 and selsyn systems 5, 6 operating on all the searchlights 3, 3<SP>1</SP>, 3<SP>11</SP>. Movement of the transmitting rotors is reproduced by the receiving rotors which by means of cams 15 and reversing switches 16 control the motors 17 to rotate the searchlights and the "stators" until the rotors open the driving circuits. Introducing relative angular displacements; scanning. Fig 2 shows an arrangement for control of searchlight beams having the same elevation but with beams fanned in azimuth, and for scanning, by synchronously varying the elevation. The azimuthal transmitters 5 have their rotors controlled by handle 4 whereas their "stators" are also given angular displacements by connections to a lever 25 pivoted at a point 25<SP>1</SP> corresponding to the central transmitter 5 and controlled by a zero sliding and rotating cam 28 operated as to its sliding movement by handle 46 to adjust the spread, which may be reduced to zero. By this means, displacements are given to the stators which increase in opposite directions from the central stator to the outer stators. The rotors 29 of the elevation transmitters are controlled by handle 30 which is also geared to the cam 28 to vary the position of lever 25 in accordance with elevation. A common elevation transmitter may be used. The seachlights are given superimposed elevational scanning movement by motor 36, driving a crankshaft 32 which oscillates the "stators" 29 by means of levers 33, links 39 and toothed gearing 37. The motor 36 is started bv switch 36<SP>1</SP> and its speed controlled by variable resistance 40. In order to prevent the indicator 12 from responding to scanning movements, compensation is effected by potentiometer 42 the arm of which is oscillated in synchronism with the stators. The scanning angle is adjusted by slotted connections between links 39 and levers 33. A similar arrangement may be used for beams having the same azimuthal angle but fanned in elevation and with azimuthal scanning which may be applied to the rotor of the azimuth transmitter by a differential gear, but a modified arrangement for this purpose is shown in Fig. 3. The common azimuth transmitter 5 has its rotor adjusted by handwheel 4 and its "stator" oscillated by motor 47 for scanning purposes. The motor also drives disc 50 carrying a pin 51 which oscillates a lever 52 whereby a toggle or like reversing switch 5 is controlled to reverse the drive at intervals depending on the position of the switch lever relatively to a cam slot 63 in lever 52. The switch 57 is moved horizontally to screw 60 rotated by gearing 61, 62 from the elevation control handle so that the angle of scan increases with elevation. Manual adjustment of the setting is effected by screw 64. In a further modification, Fig. 4 (not shown) spread is effected at the receivers by superimposing on the angles transmitted, variable and adjustable angles determined by spring controlled levers and combined with the transmitted angles by differential gearing. The levers may be brought into operation by control from the common station and may also be subject to control by the receivers to compensate variation of azimuthal spread with varying elevation. The levers may also be subject to control from the central station to change the form of the beam.