2600: The Hacker Quarterly

The magazine's name comes from the phreaker discovery in the 1960s that the transmission of a 2600 hertz tone – which could be produced perfectly with a plastic toy whistle given away free with Cap'n Crunch cereal, discovered by friends of John Draper – over a long-distance trunk connection gained access to "operator mode," and allowed the user to explore aspects of the telephone system that were not otherwise accessible.