GB248189A - Improvements in or relating to the method of and apparatus for determining the position of concealed guns or other sound producing devices - Google Patents

Abstract

248,189. Schier, J. March 19, 1925. Locating sounds. - In apparatus for locating guns or other sound-producing devices, in which microphones located at various points transmit current impulses to a central station where the impulses are recorded on a paper strip, the voltage of the impulses is increased bv transformers, the resulting alternating impulses are rectified and amplified by thermionic devices, and the direct-current impulses thus produced actuate recording pencils through electromechanical means. The electromechanical recording device preferably comprises a Johnsen-Rahbek device, having a semi-conducting revolving roller around which pass thin metal bands, the spindle of the roller being connected to the movable contact of a potentiometer and to the central point of a star-connected series of high resistances, and each metal band being connected to the outer end of one of the resistances and to the anode of one of the amplifiers. The microphones A, B, C are in circuit with batteries and with the primary windings of transformers E, F, G. One secondary terminal of each transformer is connected to the grid of one of the thermionic valves e, f, g and the other terminal to the corresponding filament. The filaments are connected in parallel to a battery H and to the negative terminal N of a battery of 120 volts. The anodes L of the valves are connected in star connection through high resistances W<1>, W<2>, W<3> to the movable contact Q of a potentiometer P connected across the high-voltage battery. The centre point of the star is connected to the spindle R of a revolving agate roller S, around part of the circumference of which pass thin metal bands T<1>, T<2>, T<3>. Each band is connected to the outer end of one of the resistances, and is attached to the upper end of a lever t<1>, t<2> or t<3>, the lower end of the levers carrying pencils s<1>, s<2>, s<3>, which bear against a paper strip moved at constant speed over a cylinder w. The metal bands are held against the agate roller by springs u<1>, u<2>, u<3>, the tension of which is adjustable. An additional pencil may be used to indicate the speed of the paper strip. Preferably the ratio of the speed of the latter to the velocity of sound is equal to the scale of the map on which the positions of the microphones are marked, so that the actual distances apart of the records of one sound on the strip are equal to the differences in the distances on the map of the source of the sound from the microphones affected.