A playback error associated with overwriting on a narrow-width track is prevented from occurring in the overwritten portion. A signal generator (11) generates a signal of a predetermined data pattern that stabilizes the operation of a synchronizing pulse generator of a playback system (shown in a separate figure). A timing generator (4) switches over a switch (12) to the output of the signal generator (11), at least a period of time equivalent to writing of one track before the main signal is input. When a signal of the predetermined data pattern from the signal generator (11) has been output, the timing generator (4) switches over the switch (12) to the main signal. The playback system includes a circuit which discriminates between the predetermined data pattern and the main signal data from a playback signal generated by playing back a record on a magnetic tape (T).