DATA RECORDING AND REPRODUCING DEVICE

PURPOSE:To use an inexpensive semiconductor laser of a low laser power when a overwrite system is selected. CONSTITUTION:During a data writing by an overwrite, the number of revolutions of an optical disk 15 is reduced to 1/N (where N is a natural number) of the number of revolutions during a data reading. During a data writing, a switch 26 is operated along a broken line as shown in the figure and a reference signal which is divided to 1/N is supplied to a driving circuit 22. Thus, the number of revolutions of a disk becomes 1/N. During an overwrite, a write head 28 is supplied with recording control signals which generate an alternating magnetic field corresponding to write data and a semiconductor laser is supplied with on off signals which have the same period with that of a data transfer rate. When the number of revolutions of the disk becomes 1/N, the laser power of the semiconductor laser used is greatly reduced and a seimiconductor laser of low laser power is used.