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UA unmanned aircraft
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UA unnumbered acknowledgment
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UART universal asynchronous receiver transmitter
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UAS unmanned aircraft system
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UAT universal access transceiver
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UATP universal air travel plan
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UAV unmanned aerial vehicle
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UBI uplink block identifier
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UCAV unmanned combat aerial vehicle
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UCD universal cockpit display
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UCI user computer interface
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UD user data
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UDF unducted fan
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UDP user datagram protocol
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UHF ultra-high frequency
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UI unnumbered information
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UIR upper information region
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UL uplink
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ULV ultra-low voltage
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ULWG upper layer working group
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UML unified modeling language
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UMTS universal mobile telecommunications system
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UP universal platform
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UPRM universal platform resource management
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UPS uninterruptible power supply
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UPSMS UPS management supply
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URET user request evaluation tool
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URL universal resource locator
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USB universal serial bus
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USC United States code
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USCG U.S. Coast Guard
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UTC universal time coordinated
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UTP unshielded twisted pair
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UV ultraviolet
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UUT unit under test
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UWB ultra wide-band