underloadundermodulationundersamplingunderscoreundersea cableundershootundervoltage alarmunderwater antennaunderwater background noiseunderwater laser scannerunderwater mineunderwater mine coilunderwater mine depth compensatorunderwater signalunderwater sound communication setunderwater sound projector projectorunderwriters laboratories lncundestructive testunequalunequal protectionunforces networkungroundeduniconductor waveguideunidimensionalunidirectionalunidirectional antennaunidirectional circuitunidirectional couplerunidirectional currentunidirectional hydrophoneunidirectional log periodic antennaunidirectional microphoneunidirectional networkunidirectional transduserunidirectional voltageunifiedunified machine theoryunifilaruniformuniform distributionuniform fielduniform lineuniform plane waveuniform transmission lineuniformityuniformlyuniformly distributed circuituniformly stableunijunctionunijunction transistor
