U
UA: User Agent.
UART: Universal Asynchronous Receiver/Transmitter.
UBR: Unspecified Bit Rate.
UDLC: Universal Digital Loop Carrier.
UDP: User Datagram Protocol.
UHF: Ultra High Frequency.
UI: Unit Interval or User Interface.
U interface: An interface within ISDN which defines the boundary between the Network Termination Type 1 (NT1) and the two wire local loop from the Central Office (CO). The NT1 connects to the Customer Premises Equipment (CPE) and the U interface meets the legal requirement of ensuring that the customer equipment is managed separately from the PTO’s network. See also V interface.
UIT: Union Internationale des Telecommunications.
UL: Underwriters Laboratory.
ULF: Ultra Low frequency.
ULSI: Ultra Large Scale Integration.
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