ABSTRACT
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 be-
tween 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.
