NT1

In ISDN, the logical interface to the carrier side of the connection, performing such functions as signal conversion, synchronization, multiplexing, frame alignment, echo cancellation, line maintenance, and performance monitoring of the local loop. Such functions correspond to Layer 1 (Physical Layer) of the OSI Reference Model. See also Echo canceller, ISDN, local loop, multiplexing, NT, NT2, OSI Reference Model, and synchronization.