Patent GB-122418-A (GB)
Title: Improvements in or relating to Methods and Apparatus for Signalling and otherwise Utilizing Radiant Impulses.
Inventor: FESSENDEN REGINALD AUBREY
IPC: G01S17/02
Filed: 1919-01-14
Abstract: 122,418. Fessenden, R. A. Jan. 14, 1918, [Convention date]. Receiving and detecting audible signals; lamp and flash signals; reflector signals; buoy signals.-Signalling is carried out by employing a reflector formed of three surfaces each at right-angles to the other two which is used to reflect waves of light, sound, electricity, &c., back to the place of origin independently of the position of the mirror provided that the waves to be reflected enter the solid angle between the three surfaces. The invention is described in connexion with signalling from advanced positions to bases during an attack from aeroplanes, or for locating the position of buoys, and in connexion with wireless telegraphy, and means for producing and detecting sound waves of a frequency above the limit of audibility. As shown in Figs. 1 and 4 applied to an optical signalling system between an advanced position and a base, &c., the forward operator is provided with a reflector 14 formed of three surfaces 11, 12, 13 which are plane mirrors which may be formed with a hole 20<1>, at the point of intersection. The reflector 14 is mounted on a rod 15 to which is fitted a shutter 16 which may be employed to send messages back to the rear position at which the transmitting lamp 22, reflector 23, and shutter 21 are situated. A telescope 24 is employed, and when this is directed towards the reflector 14, the reflected light is seen. The shutters 21, 16 can then be used to transmit messages. The forward operator carries the reflecting device only, and is thus not impeded. A mirror 17 may be mounted on the rod 15, and the device is then usable as a periscope in conjunction with the mirror 11. The shutter 16 can be worked from a trench without exposing the operator. The mirror may be formed of a glass tetrahedron with three silvered reflecting surfaces, the base being formed of plane glass, and, if desired, a small part of the glass at the intersecting corner is ground away to serve the same function as the opening 20<1>, Fig. 4. Ultra-violet rays may be used for night signalling, and detectors such as fluorescent screens of quinine sulphate may be used at the position 20<1>, or at the object glass of the telescope. A number of reflectors as 14 may be attached to a buoy, and bv means of a searchlight it may be picked up by an observer on a ship without mistaking a shore light for a buoy light, and without indicating to an enemy the position of the buoy. As applied to wireless telegraphy, the waves produced by conductors 26, 27, Fig. 6, an audion or pliotron 28, and a source of electric power 29, are reflected by a mirror 14, and a metal shutter 16 can interrupt the reflected waves before they reach a receiving device comprising conductors 30, 31, receiver 32, and a double telephonic head receiver 33. For utilizing sound waves of high frequency, these may be produced by a diaphragm 40 operated by transmitting high frequency alternations through a condenser system 39, a local battery 38, and in some cases through a telephonic transmitter. The receiving apparatus is similar to the transmitter, and a shutter 16 is used to send the signals from the trench position. The high frequency alternations are produced by a pliotron generator or a high frequency dynamo. The sound waves may be produced as described ' in Specification 18765/13. The invention claimed is limited, as regards the application of the invention to light waves, to waves of mono-chromatic light.