| 摘要 |
A digital circuit for generating a linearly increasing signal is provided for controlling the level of a recording A. C. bias signal. The digitally controlled bias signal is mixed with an analog signal of a known frequency and constant level and recorded. The circuit detects and stores a recording bias level corresponding to a reproduce signal envelope level, equal to an obtained peak level adjusted with respect to a known overbias level. The circuit compensates the detected recording bias level with respect to distance between the recording and reproducing heads to obtain an optimum recording bias level. The detected bias level remains stored and unchanged during power supply interruption.
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