GB247991A - Improvements in acoustic apparatus - Google Patents

Abstract

247,991. Hewitt, A. Feb. 19,1925, [Convention date]. Void [Published under Sect. 91 of the Acts]. Magnetic instruments; m o u t h - pieces ; loudspeakers. -A recorder and reproducer which can operate directly or electromagnetically or both at the same time, and which is also applicable as a telephone transmitter or a loud speaking receiver, comprises a casing carrying a stylus bar having a flexible portion to which is attached a diaphragm and also an armature co-operating with an electromagnetic system. As shown, a flexible rod 26, Fig. 2, extending from a stylus bar 27 mounted on a knife edge 30 on a cross bar 29 of a casing 10 carries, at its free end, a diaphragm 28 and, intermediately, an armature 25 projecting through a coil 24 on a spool 23a housed within opposing U-shaped poles 22 of a circular magnet 20. The casing 10 is fitted with a dished and apertured disc 12, a vulcanized rubber liner 14, an end ring 16 supporting a rubber ring 17 embracing the diaphragm 28, and a bossed disc 19 apertured to engage the tone arm, or, when the device is used as a transmitter only, to receive a bush carrying a mouthpiece or horn. The disc 12 supports terminals 36 for the coil 24 and for the transmission wires 37. The stylus bar 27 is held against the knife edge 30 by spring fork proiections 32, Fig. 5, on each side engaging under T-shaped lugs 31 upstanding from the cross bar 30. By means of the device direct sounds impinging on the diaphragm can be recorded and electrically transmitted simultaneously, or recorded or transmitted alone or recorded sound can be reproduced both directly and in the form of current variations simultaneously, the transmitted sound currents in either case being, if desired, amplified for reproduction bv a loud speaker. Further, the device when applied to the tone arm of a gramophone serves as a loud speaker for a broadcast receiver.