Notes on the Network
Notes on the Network was a publication of the American Telephone & Telegraph Company (AT&T) that outlined the state, technology, and operating principles of the public switched telephone network in the United States and Canada, and the other member regions of the North American Numbering Plan and its predecessors. The origins of publication date back to the 1945 communications about Nationwide Operator Toll Dialing disseminated by AT&T to the Bell System companies and to the independent telephone operators via the Dial interexchange Committee of the United States Independent Telephone Association (USITA).