| 摘要 |
PURPOSE:To simplify and minimize a circuit composition by changing a magnetic head from recording or reproducing to erasing with the ON/OFF of a semiconductor switch and the control of a direct current constant-current source. CONSTITUTION:When the attenuating voltage of a prescribed waveform is impressed from an attenuating voltage generating circuit 28 to the base of a transistor (TR) 1, the same waveform of attenuating currents I1, I2, I3 flow in the TRs 2-4, and emitter resistance R2, R3 and R4 retain I1=I2=I3 by means of a negative feedback action. The attenuating currents I1-I3 are fixed currents which are fixed by the attenuating voltage impressed to the base of the transistor TR1. When a command switch 20 is inputted in the erasing side to lower the PR terminal of a flip-flop 25, the inputted pulse 27 of a CP terminal is divided, and two of switching TR5 and TR6 repeat ON/OFF alternately every time the pulse 27 is inputted. Thus, the erasing current flows. On the other hand, when the command switch 20 is inputted in the recording or reproducing side to increase the PR terminal to a high electric potential, recording or reproducing can be executed.
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