ISDN REFERENCE POINTS

REF. POINT

DEFINITION

R

·         between the TE 2 (Terminal Equipment 2) and the TA (Terminal Adapter)

S

·         between the ISDN CPE (either the TE 1 or the TE 2/TA) and the NT 1

T

·         between the customer PBX (NT 2) and the local loop termination (NT 1)

S/T

·         between the ISDN CPE and the local loop termination (NT 1) - S/T integrated interface for BRI only

U

·         Telco network termination up to the NT 1 device;  also referred to also as U-Loop