A blue box is an electronic device that generates the in-band signaling tones formerly generated by telephone operator consoles to control telephone switches. Developed during the 1960s, blue boxes allowed private individuals to control long-distance call routing and to bypass the toll-collection mechanisms of telephone companies,[2] enabling the user to place free long-distance telephone calls on national and international circuits.
At first the use of these techniques was limited to a small group of "phreakers", which included, among others, Steve Wozniak. After the publication of "Secrets of the Blue Box" in October 1971's edition of Esquire, interest in the topic grew tremendously, both among end-users as well as the Bell System. The practice was ruled as telephone fraud by the Bell System and the courts, and prosecuted vigorously.
Blue boxes worked because the telephone system used tones in the existing voice lines to send routing instructions, and these tones were not filtered out at the handsets. Subsequent telephone switching technologies used out-of-band signaling methods in the form of Common Channel Interoffice Signaling (CCIS) in a separate channel not accessible to the caller. Blue boxing stopped working as these systems were deployed.
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Release v2.0.0 codename:
Blue Box