GB701032A - Improvements in and relating to electron discharge apparatus for producing modulatedelectric currents - Google Patents

Abstract

701,032. Microphones &c. WTLLS, H. G. March 27, 1950 [March 29, 1949], No. 8509/49. Class 40 (4) [Also in Group XL (a)] Cathode ray apparatus for producing modulated electric currents comprises means for deflecting the beam over two anode members arranged edge to edge, wherein the juxtaposed anode edges are formed' with intermeshing serrations or undulations having oblique or curved faces so as to obtain high sensitivity. The deflecting means may comprise an electrostatic member coupled to a diaphragm or functioning as a diaphragm for receiving sound waves, or coupled to a moving body. In a further modification the electrostatic or electrodynamic means usually employed for focussing the stream may be coupled to the diaphragm or moving body. Particular applications are to microphones and electrical pick-ups such as radiogram pick-ups or pick-ups for detecting movements of parts of a structure under load or subject to vibrations or temperature changes. The device can be used to operate a loud-speaker direct. In the device illustrated, the envelope 1, Fig. 1, is of flat rectangular form and has directly or indirectly heated cathode 2, parabolic negative " reflector " electrode 18, beam forming and concentrating electrodes 10, 16 comprising one or more plates and rectangular frames respectively for forming a ribbon beam, main anodes 3, 4 and an auxiliary centralising anode 19. Two negatively biased " deflector " plates 21, 22 connected by a mechanical coupling 23, are coupled to the diaphragm or other movable body by coupling 24. The plates 21, 22 are thus oscillated up and down and this is stated to vary the current in the output transformer 7, 8. The Provisional Specification states in addition that the deflecting means may be a coil instead of a plate or plates. The deflecting means is arranged as near as possible to the cathode. The movement of the deflecting means may be modified to assist in producing a desired wave form. The deflecting means may be driven by a vibrator or motor or, alternatively, instead of moving the deflecting means, an alternating or varying potential may be applied thereto.