DDD Hear it!

DDD definition - telecom
A feature of the public switched telephone network (PSTN) that allows a subscriber to dial a long distance telephone number directly, i.e., without the intervention of an operator. DDD was introduced by the Bell System in 1951, and is virtually ubiquitous today. See also long distance and PSTN.

Webster's New World Telecom Dictionary Copyright © 2008 by Wiley Publishing, Inc., Indianapolis, Indiana.
Used by arrangement with John Wiley & Sons, Inc.

Comments
Improve this definition.
Do you have more to add? Share your linguistic knowledge or observation.
/Register to save your comments.