The VU meter has become the universal standard level indicator for practically all audio frequency transmission
systems. VU meters are for the measurement of sound or noise levels - including broadcast monitoring, use with
public address of communication systems, and in all instances where volume level measurements are to be made. It is also being used for the measurement of noise level and other audio frequency energy where established dymanic characteristics of the instrument give a common result for measurements taken in different laboratories.
VU INSTRUMENT DETAILS
The VU meter is designed to read zero VU or 100% with 1.228 volts applied to the instrument and the 3600 ohm
series resistance; this represents 4 DB above 1 milliwatt in 600 ohms. The combination of a special copper oxide
rectifier and an extremely sensitive movement with special magnetic system gives very high sensitivity.
STANDARDIZED INSTRUMENT SCALE
The VU instrument has become so universally accepted that numerous requests have been received to add other
scale ranges to the VU Scale for special purposes.

TYPE A SCALE
The "A" Scale reads "-20 to +3" in type on the top of the arc, with "0-100" on the bottom of the arc in type.
TYPE B SCALE
The "B" Scale reads "0-100" in type on the top of the arc, with "-20 to +3" in type on the bottom of the arc.