Automatic adjustment of biasing current for recording sound by three-head type tape-recorder

Abstract From the Canadian patent

The invention provides a method of automatically establishing the proper adjustment of biasing current for recording sound with a three-head type tape-recorder which is equipped with a separate recorder head, reproducer head and eraser head so, that sound which is recorded by the recorder head on a running magnetic tape may be immediately reproduced by the reproducer head immediately downstream of the recorder head the method com-, prising the steps of: generating a composite calibration signal by mixing a lower frequency signal and a higher frequency signal having sound level identical with each other recording the com-, posite calibration signal while chronologically consecutively …