Notes on the Network is a publication of the American Telephone & Telegraph Company (AT&T) that outlines 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.
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).
[1] In 1955, AT&T published the first extensive edition under the title Notes on Nationwide Dialing,[2] which was updated the following year (1956) under the title Notes on Distance Dialing.
In 1983, shortly before the 1984 divestiture of AT&T, Telecom-Canada published Digital Network Notes, an update and companion volume to the 1980 AT&T Notes on the Network, with more specific information for the Canadian territory.
It provided a detailed analysis of the history of analog and digital telecommunications, and offered references for the design, implementation, and operation of digital networks.