Abstract: A recording device for recording information upon optically modulated overwritable magneto-optical recording medium including four magnetic layers first records DC "1" and then a test signal at high and low recording laser power levels upon a test track of the recording medium. The high and low recording laser power levels are successively modified to scan a two-dimensional region of the high and low recording laser power levels, and the optimal high and low recording laser power levels are determined on the basis of the reproduction signal levels corresponding to respective combination of high and low recording laser power levers. The reproduction signal levels are represented upon the .alpha.-K plane which is divided into six characteristic regions, The optimal combination of high and low recording laser power levels is determined as a representative point within the region of correct reproduction with a predetermined allowance.

Abstract: An impedance meter with improved measurement accuracy obtained by controlling the level of the signal source. The impedance meter comprises a signal source, feedback amplifier, synchronous detector, A/D and control logic. The source level is maintaind by the control logic at a predetermined value by measuring the output of a synchronous detector and intermittently adjusting the level of the source thereby compensating for variations in test object's impedance. Control logic algorithms employed include successive substitution, bisection and linear interpolation.

Abstract: Diphenols, alkyl ethers and aryl ethers of diphenols are produced by subjecting phenols, alkyl ethers and aryl ethers of phenols to oxidation with an organic per-acid in the presence of at least one member selected from the group consisting of acetyl acetone and acetonyl acetone as the catalyst.

Abstract: A color image projecting apparatus having three cathode ray tubes which produce different respective color images and including two projecting lenses. A first primary color image reproduced on a first cathode ray tube is projected on a screen through a first projecting lens, and second and third primary color images reproduced on second and third cathode ray tubes, respectively, are synthesized by a dichroic mirror and then projected on the screen through a second projecting lens. In this case, the projecting axes of the first and second projecting lenses are arranged to converge two images passed therethrough on the screen.