ERASION PREVENTION AND ERASION PREVENTION RELEASING CIRCUIT

摘要

PURPOSE:To prevent or release an erasion by a track unit with respect to a floppy disk, by detecting an erasion inhibiting signal recorded in a track and inhibiting an erasion to its track, and also, releasing the erasion inhibition by overlapping and recording an erasion inhibition releasing signal. CONSTITUTION:At the time of reproducing, switches SW1, SW4 are switched by an instructing signal (b) which an instructing signal generating circuit 60 provided with monostable multivibrators 61, 62 output by a necessary timing, and from a reproducing output by a magnetic head H, whether an erasion inhibiting signal C' of each track exists or not is detected by an erasion inhibiting signal detecting circuit 90. As for the track in which the erasion inhibiting signal is detected, a switch SW2 is controlled through a CPU 100, and an erasing signal from an erasing signal generating circuit 80 is not applied to a head H. In the same way, when an erasion inhibition releasing signal C' of oscillator 70 is selected through the switches SW1, SW2, the signal C' is overlapped and recorded onto the erasion inhibiting signal and the erasion inhibition of its track is released, and the erasion inhibition and the erasion release can be executed by a track unit.