| 摘要 |
PURPOSE:To discriminate a recording speed by detecting an envelope of the reproduced output of a rotary magnetic head in the state where a magnetic tape is run at a prescribed speed at a reproducing start time and shaping the waveform of the detection output and measuring the period of one level of the shaped output with a timer. CONSTITUTION:When a reproducing key is operated, a control circuit 28 generates a reset pulse P1 to reset a flip-flop 29. A Q' output of the flip-flop 29 goes to the high level, and the control circuit 28 controls a motor driving amplifier 26 so that the tape running speed coincides with the LP mode. When data is recorded on a magnetic tape 1 in the LP mode, a counter 34 does not count FG pulses P3 at all. When data is recorded on the magnetic tape 1 in the SP mode, the counter 34 counts FG pulses P3 while pulses are in the low level. The envelope of the reproduced output of a pilot signal is detected, and the period of the low level is measured by the counter 34 to discriminate the recording speed.
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