Table of Contents
Whistling 2600 Hz
| Field | Phone Phreaking |
| Went Obsolete | Later in the 20th Century, possibly 1980s |
| Made Obsolete By | The introduction of Signaling System #7 |
| Knowledge Assumed | Absolute pitch or possession of a small toy whistle from Cap'n Crunch breakfast cereal |
| When useful | Illegally Dialing free long-distance phone calls (Also known as Phone Phreaking) |
In the early days, sending a 2600 Hz tone over the telephone is required to (illegally) make free long-distance phone calls (infamously known as Phone Phreaking).
The act of whistling 2600 Hz can be done by a person with absolute pitch (being able to accurately produce a musical note without the benefit of a known reference) or using the “Cap'n Crunch” toy whistle.
At one point in the 1960s, some of the Cap'n Crunch breakfast cereal included a small whistle that coincidently generated a 2600 Hz tone, which can be used for Phone Phreaking. Blowing the whistle with one of the whistle's two holes covered would produce a 2600 Hz tone.
