Intercepting a telephone line to make long distance calls or insert embarrassing comments. Phone phreakers would use a tone generator to bypass charges in the 1960s and 70s when telephone companies charged for long-distance phone calls between states in the U.S. Telephones could be controlled by specific tones such as a 2600 Hz signal. It is notable that in their youth Apple co-founders Steve Wozniak and Steve Jobs were phone phreakers. See
hijacking and
Phrack.