In the early 1970s, a phone phreak nicknamed "Captain Crunch" became famous for a startling trick: a toy whistle packaged in Cap'n Crunch cereal boxes produced a perfect 2600 Hz tone — the exact frequency AT&T used to signal an idle line — letting him fool the phone system into handing him free long-distance calls (opens in new tab)

In the early 1970s, the most powerful machine on Earth was the American telephone network. It was vast beyond comprehension — millions of miles of copper, tens of thousands of switches, the largest interconnected system human beings had ever built. And it was held together, in part, by sound. The network used audio tones, sent […]