In the U.S. implementation of a CCITT X.25 network , the first three digits of a network terminal number (NTN). Note: The 10- digit NTN is the specific addressing information for an end-point terminal in an X.25 network.
DATA NUMBERING PLAN AREA (DNPA)
Meaning of DATA NUMBERING PLAN AREA (DNPA) in English
Telecommunication standard terms English vocab. Английский словарь стандартных телекоммуникационных терминов. 2012