A Cap'n Crunch 2600 Hz whistle, Deutsches Technikmuseum

1971

The actual cereal-box whistle displayed as a museum object in Berlin. Holding the real, cheap plastic object next to the phone system it defeated is the whole point of the phreaking story. The 2600 Hz exploit was publicised by Ron Rosenbaum's 1971 Esquire article 'Secrets of the Little Blue Box'. The subject dates from 1971; the photograph itself is later.