The calibration of audio magnetic tape recording presents various problems with respect to accuracy. One problem involves the calibration of the standard recording level of the reference signal and another the calibration of the frequency characteristics of the lower and higher ranges. To solve these problems, we have discovered a new method related to the reference signal which is both practical and precise compared with the ordinary method in the field of magnetic tape recording equipment. We are also introducing a new method for the calibration in the lower range by using a single turn "loop head," and also calibration in the higher range by measuring the "spacing loss" in relation to the surface roughness on the magnetic head. Finally an explanation is given of the newly developed test tape recording process, which is controlled by a "mini-computer system."
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