| 摘要 |
PURPOSE:To perform secure erasure by providing a function which records a marker signal of specific frequency at a running position of a recording meidum in recording mode and a function which detects the marker signal in reproducing mode. CONSTITUTION:When a switch 1 is operated in recording mode, a signal of frequency generated by an oscillator 3 is supplied to a timer 5. The timer 5 applies the signal to a recording head 6 for a preset time and records it on a tape at the marker signal. The tape is rewound and run again in reproducing mode and the tape is traced by a detection head 7, but the detected marker signal is applied to an integration circuit 10 through a band-pass filter 8 at every time and converted into a DC signal. Each DC signal is applied to a detector 14, which decides whether the DC signal is detected for the 1st time or the 2nd time and outputs an erasure signal SE or erasure stop signal SS. Consequently, the signal recorded in a specific section is erased securely. |
