Direct distance dialing (DDD) is a telecommunications service in North America by which a caller may call any other subscriber outside the local calling area without operator assistance. DDD was introduced in the United States in 1951, on a trial basis, with service from Englewood, New Jersey.
Direct distance dialing (DDD) is a telecommunications service in North America by which a caller may call any other subscriber outside the local calling area without operator assistance. DDD was introduced in the United States in 1951, on a trial basis, with service from Englewood, New Jersey.
Source: Wikipedia "Direct distance dialing" · CC BY-SA 4.0
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