Patent GB-551376-A (GB)
Title: A method whereby the position of a wireless transmitter is automatically located, and the position is indicated on map by a point of light
IPC: G01S1/02
Filed: 1941-08-18
Abstract: 551,376. Electric indicating systems. THORLEY, J. Aug. 18, 1941, No. 10463. [Class 40 (i)] [Also in Groups XL and XXXVII] Means for indicating the position of a wireless transmitter by means of a light-spot on a map comprises in combination two discs I, M with diametrical slots N\ N<SP>2</SP>, each being pivoted beneath the point on a translucent map A corresponding to the position of two spaced receiving stations, a light source 01 beneath the discs, a rotatable frame aerial at each receiving station and means for imparting angular movements to the frame aerials and the discs and for illuminating the lamps so co-ordinated that periodically the slots simultaneously extend in relation to the map in the same directions as those of the transmitter from the two receiving stations and at the same instants the light source is caused to operate, whereby the light passing through the intersecting portions of the slots forms an intermittent spot on the map which indicates the position of the transmitter. In the form shown, a frame aerial B situated at one station is automatically rotated to its position of minimum reception by a reversible motor controlled by a relay, Fig. 3, operated by currents derived from the received signals, and is connected by gearing to the disc I so that the latter is simultaneously adjusted so that the slot N<SP>1</SP> in it indicates in relation to the map the bearing of the transmitter from which the signals are being received. The second disc M is continuously rotated by a motor in synchronism with the rotating frame aerial C, Fig. 8, at the other receiving station. The synchronizing means comprise a disc e, Fig. 9, secured to the rotating shaft f of the aerial and carrying contact segments co-operating with contacts h to control the modulator of a transmitter j, so that the carrier radiated from a transmitting aerial o is divided into synchronizing pulses which after rectification amplification at the first station are supplied to field coils W controlling a synchronizing armature H which controls the rotation of the disc M. As the frame C passes through its positions of minimum reception the received signals, which are detected and amplified in a receiver d, cause the operation of a relay k in the output circuit of a valve I, H, n, so causing the modulator of the transmitter j to reduce the radiation from the aerial o. This causes a relay in the receiver circuit at the first station to close the circuit of the lamps o<SP>1</SP>, so that they light at the moments the slot N<SP>2</SP> in the disc M lies in relation to the map in the direction indicating the bearing of the transmitter from the frame aerial C. An intermittent light beam thus passes through the overlying portions of the slots N\ N<SP>2</SP> and forms a spot on the map indicating the position of the transmitter. To adjust the disc M so that the slot N <SP>2</SP> is correctly oriented in relation to the orientation of the frame aerial C, two intervals w in the segments on the disc e cause suppression of the carrier radiated from the aerial o for longer periods that those between the synchronizing pulses, causing two operations of the relay controlling the lamp circuit which, when the adjustment is correct, occur as an aperture n<SP>1</SP> in the disc M passes over two indicator lamps o<SP>2</SP> in series with the lamps o<SP>1</SP>, so that the flashes can be seen through the aperture. The relay controlling the lamp circuit does not respond to the normal synchronizing pulses. In a modification the frame aerial C at the second station is, like that at the first station, automatically turned to its position of minimum reception, and angularly adjusts brushes in relation to a contact ring formed with diametrically-opposite gaps and carried by a rotating disc, which disc also carries segments for causing the emission of pulses by which the rotation of the disc M is synchronized with it, as in the first form. As the gaps in the contact ring pass under the brushes of which the position is determined by the orientation of the aerial, the carrier wave is reduced as in the first form to cause operation of the relay to close the lamp circuit at the first station. The disc M and the lamps o<SP>1</SP> may be replaced by a tubular lamp or lamps rotatably mounted and operated so as to take the place of the slot N<SP>2</SP>. The synchronizing and lamp-illuminating impulses may be conveyed from the second station to the first by communication lines instead of by radiated signals, and the use of synchronizing impulses may be avoided by the use of controlled frequency supply' mains. The relay shown in Fig. 3 for controlling the reversible motor which orients the frame aerial comprises a bar V suspended or pivoted at its upper end and carrying armatures y<SP>1</SP>, y<SP>2</SP> and contact strips co-operating with fixed contacts P<SP>1</SP> ... P<SP>4</SP>. The magnet winding Q is in the output circuit of a valve amplifier, and on the reception of signals by the frame aerial the armature y<SP>2</SP> (which is closer to the pole s<SP>2</SP> than the armature y<SP>1</SP> is to the pole s<SP>1</SP>) is attracted, causing bridging of the contacts P<SP>3</SP>, P<SP>4</SP> and consequent rotation of the aerial towards the position of minimum reception. When the current in the coil Q falls below a definite value the bar V is released and swings so that it bridges the contacts P<SP>1</SP>, P<SP>2</SP> momentarily reversing the motor so that it brings the frame aerial to rest in the position of minimum reception. If this position is overshot, the armature y<SP>1</SP> is attracted to keep the contacts P\ P<SP>2</SP> bridged for a sufficient time for the motor to return the frame to it.