ADTRAN 61200051L1, 1200051L6, 1200051L2, 1200051L5 user manual NT1

Glossary

NEXT (near-end crosstalk)

Unwanted energy transferred from one circuit to an adjoining circuit. Occurs at the end of the transmission link where the signal source is located. The absorbed energy is usually propagated in the direction opposite to the absorbing channel’s normal current flow. Caused by high-frequency or unbalanced signals and insuf- ficient shielding.

non-ISDN line

Any connection from a CPE to a SPCS that is not served by D-channel signalling.

non-ISDN trunk

Any trunk not served by either SS7 or D-channel signalling.

NT1

Network Termination 1. A unit that provides physical and electromagnetic termi- nation of the U-interface 2-wire transmission line, converts between Layer 1 for- mats used at the U- and T- reference points, and performs some maintenance functions.

packet mode

Refers to switching of packets of information for different users by statistically multiplexing them over the same transmission facilities. ISDN packet mode capa- bilities are based on CCITT Recommendation X.25 procedures.

point-to-point

Describing a circuit connecting two points directly with no intermediate process- ing nodes or computers (although switching facilities could exist). A type of con- nection that links two logical entities (i.e., phone-line circuit).

S-interface

S-reference point. The interface that connects an ISDN terminal (TE1) or Terminal Adapter (TA) to the NT2 reference point as defined in the I.411 Recommendation.

SPCS

stored program controlled switch. A digital switch that supports call control, rout- ing, and supplementary services provision under software control. All ISDN switches are SPCSs

SDLC

synchronous data link control. A data communications line protocol associated with the IBM System Network Architecture. SDLC is a bit-oriented protocol (not a character-oriented protocol) that includes multiple block error checking and full duplex line operation.

sync bits

Framing or synchronizing bits in synchronous transmission.

61200051L1-1D ISU 2x64 Dual Port ISDN Service Unit User Manual 141