GB365639A - Improvements in or relating to methods of and apparatus for recording and reproducing sound - Google Patents

Abstract

365,639. Recording and reproducing sound. ELECTRICAL RESEARCH PRODUCTS, Inc., 195, Broadway, New York, U.S.A.-(Assignees of Keller, A. C. ; 2197, Cruger Avenue, New York, U.S.A.) Oct. 23, 1930, No. 31877. Convention date, Oct. 30, 1929. [Class 40 (iv).] In a system for recording and reproducing sound from separate sources each comprising a frequency range sufficient for good reproduction these are received on separate receivers such as microphones and the currents produced in the second and further receivers are displaced in the frequency scale by modulation so that the several sound sources are represented by a progressive series of frequency bands separated by intervals, the currents from which collectively influence a recorder and are thereby recorded in a single groove. In reproducing, the output from a single pick-up is selectively divided so that the part representing the modulated currents passes through corresponding demodulating circuits which deliver current corresponding to the original sound sources to separate loud-speakers. As an example applied to three sound sources each having a frequency band of 60-4500 cycles, one source is taken by receiver 1, as shown in the Figure, delivering through amplifier A, a second source taken by receiver 2 passes through an amplifier A and is modulated by a known modulator 8 and oscillator 9 to a frequency range of 5060-9500 and the third source taken by receiver 3 is modulated by modulator 10 and oscillator 11 to a frequency range of 10060-14500, the currents of these three frequency ranges being superposed and fed through an amplifier 5 to a recorder 6 by which they are recorded on a disc 7. In reprod.uction, the output from the pick-up branches into three circuits two of which effect demodulation corresponding to the modulation effected in the recording circuits. Specification 363,449 is referred to. The Specification as open to inspection under Sect. 91 (3) (a) refers to the recording and reproduction of higher frequencies such as transients together with the sounds, and refers to Specification 226,338, [Class 40 (iv), Telephones &c.], and U.S. Specification 1,675,894. This subject-matter does not appear in the Specification as accepted.