UER: Union Européenne de Radio-Télévision (www.ebu.ch ).
UHF: Ultra High Frequency radio waves.
Ultrasonic: Audio frequencies above the upper limit of human hearing (approx 20,000 kHz).
Unbalanced Audio: An audio signal which consists of one "hot" signal plus the shield. This is common in home entertainment systems, as well as other systems with short audio cables. Unbalanced audio cables are prone to external interference, and are not prefered in professional situations. Related info: Balanced audio
UV: Ultra-violet light.
UV Filter: A filter which blocks out a certain percentage of ultra-violet light.