A network -provided service feature in which a call originator may, without operator assistance, call any other user outside the local calling area. ( 188 ) Note 1: DDD extends beyond the boundaries of national public telephone networks. Note 2: DDD requires more digits in the number dialed than are required for calling within the local area.
DIRECT DISTANCE DIALING (DDD)
Meaning of DIRECT DISTANCE DIALING (DDD) in English
Telecommunication standard terms English vocab. Английский словарь стандартных телекоммуникационных терминов. 2012