Abstract: A conventional display system carried on a railroad train has the problem that it cannot distribute image signal to the cars of the train when image information output means mounted in a lead car breaks down. Accordingly, a display system to be carried on a railroad train according to the invention includes: first image information output means provided in a given car in a train of a plurality of connected cars, for outputting first image information; second image information output means provided in a given car of said train, for outputting second image information; and display means provided in a given car of said train, for switchably displaying said first image information transmitted from said first image information output means and said second image information transmitted from said second image information output means.

Abstract: A conventional display system carried on a railroad train has the problem that it cannot distribute image signal to the cars of the train when image information output means mounted in a lead car breaks down.

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.