GB252078A - Improvements in methods for recording sounds - Google Patents

Abstract

252,078. Gramophone Co., Ltd., and Mittell, B. E. G. Feb. 18, 1925. Repeating and amplifying systems; systems for transmitting music &c.-In a method of recording sound by electrical means upon a plurality of record surfaces simultaneously, provision is made for varying the characteristics of each record by varying the electric circuits to the recorders. A monitoring loud speaker may be inserted in the circuit of any of the recorders. In one arrangement, electric oscillations produced by sound waves on a microphone a after transformation at b, amplification at c and transformation at s are supplied to separate circuits to actuate electromagnetic recorders h, i, and the second circuit of the second transformer s contains an impedance f acting as a potentiometer, points on which are connected to contact studs by other impedances l<1>, l<2>, l<3>, m<1>. m<2>, m<3> such that the total impedances on the circuit through any contact stud is the same and equal to that of the secondary of the transformers. The central point g of the impedance f is connected to each recorder, and by connecting the arms j, k to different contacts the recorders are actuated to produce records having different characteristics. In a modified arrangement the secondary of the sound transformer is replaced by two coils which are connected directly, or through impedance circuits and contact studs such as described, with the recorders; or the currents in the two secondary coils may be amplified and passed through further transformers before actuating the recorders. The current in the recorder may also be varied by taking tappings from a choke coil in the output circuit of the amplifier and connecting any of these to the recorder or to the input circuit of the succeeding amplifier if an additional one is employed.