The knowledge of the recorded signal amplitude on a magnetic record (which may be in the form of a tape, a disc, oτ a perforated film) has several practical uses: (1) for determining and standardizing references for the levels of audio programs on these magnetic records; (2) for specifying the recording-performance properties of magnetic media (for example, the distortion versus flux, etc); and (3) for measuring and specifying the sensitivity of reproducing heads (and also, by reciprocity, recording heads). The quantity for specifying the recorded signal is the short-circuit magnetic flux, sometimes simply shortened to flux. Several possible methods exist for measuring tape flux, but the measurement given here involves only the use of a calibrated ring-core head which is described in the reference of the standard. Note that the present standard measurement is only for "medium wavelengths". |