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150 Handbook of Intercom Systems Engineering
supply operates a string of belt pack or other user stations in an isolated, balanced mode. The
balanced system is transformer coupled into the regular unbalanced system.
V
V
The symbol for volt.
VA
The symbol for volt-ampere. A volt-ampere describes the demand on the power line without
regard to power factor or true power. This figure is more helpful in determining the maximum
load on a circuit, that has a given ampere rating.
Voltage
The term for electrical potential of electromotive force.
Voltage Drop
See IR drop.
VU
Volume Units.
VU Meter
Used to show the relative levels of signals. A change of one VU is a change of one dB. VU meters
have their 0 VU point referenced to different levels. This level may be 0 dBm, +4 dBm
(Recording Industry), +8 dBm (Broadcast Industry). In addition, correct calibration is further
involved. The VU Meter has certain characteristics tailored for monitoring sound. Generally
speaking the audio peaks are 10 dB above the indications shown on a standard VU meter due to
the lag of the meter. Some VU meters are combined with peak reading meters. Levels stated in
“VU”s generally apply to program material. Readings in dBm generally apply to a steady state
sine-wave.
W
W
The symbol for the unit of power, the watt.
Watt
A unit of electrical power. One watt is the power delivered by one volt at a current of one ampere
in a DC circuit, and one volt at one ampere with a phase angle of 0 degrees in an AC circuit.
Wave Form
A graphical representation of a varying quantity. The x (horizontal) axis usually represents time
and the y (vertical) axis usually represents amplitude, energy, or power.
White Noise
Equal noise energy per hertz.
Windscreen
A microphone cover designed to reduce extraneous noises caused by gusts of wind. Also useful
for reducing pop from speech plosives such as “b”, “p”, and “t”.
Wet Line
An intercom or telephone line that carries both audio and DC voltage / current. As opposed to a
dry line that carries only the audio.
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