Abstract: An optical system including an objective lens applies five light beams (31 to 35) generated by an optical pickup to a plurality of adjacent tracks on a signal plane of a CD-ROM. Light beams reflected from the signal plane are detected with photodetectors (PD1, to PD6), and in accordance with the detection outputs of the photodetectors (PD1 to PD5), a record data read system reads at the same time data recorded on respective tracks applied with the light beams (31 to 35), and outputs to read data in the record order of CD-ROM by preventing the read data from being duplicated or omitted. Prior to reading record data, a system controller performs an offset bias adjustment of a focus servo system.

Abstract: A magnetic tape recording signal level automatic adjustment device includes: a reproduced signal level attenuator responsive to an attenuation changeover instruction for attenuating the level of a reproduced signal from a PCM audio signal reproduction device by a predetermined quantity; and an attenuation controller responsive to a sampling instruction for comparing the reproduced signal level with a reference value and outputting the attenuation changeover instruction when the reproduced signal level exceeds the reference value.