John T. Draper, also known as Captain Crunch (after Cap'n Crunch, the mascot of a breakfast cereal), was a phone phreaker.

He discovered that the yellow toy whistle found in the breakfast cereal Cap'n Crunch emitted (with slight modification) a tone at precisely 2600 hertz -- the same frequency that was used by AT&T long lines to indicate that a trunk line was ready and available to route a new call. This would effectively disconnect one end of the trunk, allowing the still connected side to enter an operator mode.

"I don't do that. I don't do that anymore at all. And if I do it, I do it for one reason and one reason only. I'm learning about a system. The phone company is a System. A computer is a System, do you understand? If I do what I do, it is only to explore a system. Computers, systems, that's my bag. The phone company is nothing but a computer."

-- From Secrets of the Little Blue Box by Ron Rosenbaum, Esquire Magazine (October 1971)

This feature of the older phone call routing switches has long since been corrected, but it resulted in the Cap'n Crunch whistles becoming valued collector's items. Young hackers sometimes go by the handle "Captain Crunch" even today, as a result of this incident and 2600 The Hacker Quarterly is named after the frequency of the whistle.

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