[BC] VI vs VU

[Stanley Adams]

VI was the WE method of measuring a certain standard level into a certain
standard impedance.  It came about in 1922( E L Nelson) in which a dc meter
would follow the envelope of the speech pattern and relate it to some
tangible standard.  This was necessary to allow for the setting of level
standards from the basic wire loop through to a telephone handset.  Maximum
loudness with minimum distortion and transmission anomalies. 

VU became a more generally accepted standard as the meter movements changed
from the VI type with its wide ballistics to the more RMS range of a VU
where speech levels are measured, the real old NAB handbooks talk about the
differences.  Some of the real old timers on here could pontificate about it
if they so choose.



Stanley Adams
Memphis