Inventor(s): Charlin; Andre Marie Bernard, 75015 Paris, France

Applicant(s): none

Issued/Filed Dates: June 22, 1976 / Dec. 19, 1973

;Application Number: US1973000426116

IPC Class: G11B 003/04;

Class: 274/046.R

Field of Search: 179/100.4 ST,1 GQ 274/46 R

Priority Number(s): ;FR1972000045329

Abstract: A microgroove disk record for monophonic, stereophonic and tetraphonic reproduction of modulated information recorded on four separated tracks one of which corresponds to a left fore channel, another one to a right fore channel, another one to a left rear channel and another one to a right rear channel, comprising two adjacent parallel grooves one of which carries the tracks corresponding to the left fore and right fore channels and the other one carries the tracks corresponding to the left rear and right rear channels, the spacing between both channels being variable according to the modulation.

Primary/Assistant Examiners: Aegerter; Richard E.; Thaler; MIchael H.

U.S. References: (No patents reference this one)

Patent Inventor Issued Title

US2977424 Redlich 3 /1961
US3075052 Terry 1 /1963
US3118977 Olson 1 /1964
US3223789 Ooms 12 /1965

* some details unavailable

First Claim: What is claimed is: 1. A method of engraving a microgroove disk for recording modulated information such as music which may be reproduced in tetraphony and previously recorded on four tracks of a magnetic tape, comprising the steps of engraving a first groove including two separated tracks corresponding to a left front channel and a right front channel, respectively; simultaneously engraving a second groove to extend in substantially parallel and adjacent relation to the first one and including two separated tracks corresponding to a left rear channel and a right rear channel, respectively; and simultaneously with the engraving of the first groove and the engraving of the second groove varying the spacing between the first and second grooves being engraved in accordance with the amplitude of the modulation of information, the spacing being varied greater than and less than a predetermined mean spacing between the first and second grooves.

Foreign References:none (No patents reference this one)