ABSTRACT
The Standard Volume Indicator was originally developed by the Bell System around 1940 and standardized in 1942. The original Standard Volume Indicator consisted of a full-wave rectifier and a galvanometer. An important part of the Standard Volume Indicator is the attenuator circuitry connected to the meter. This passive electronic network determines the impedance and sensitivity of the complete meter. Volume indicator (VU) was originally denoted as a term designated to indicate volume. The VU meter was widely used for the calibration of, for instance, tape-based media. The precise calibration values have changed over the years with the change in tape sensitivity. Hence, the VU reading in these cases is related to the media rather than to volume or voltage.
