Probably based on the Cap'n Crunch whistle pay phone hack.

Someone correct me if I've missed a few bits, but here's the story...

First, a little history.

Payphones were common. If you're younger, you've probably seen them in movies. To operate them, you picked up the handset, listened for the dial tone (to make sure no one yanked the cord loose), inserted the amount shown by the coin slot, and then dialed. You have a limited amount of time before an automatic message would ask you to add more money. If you dialed a long distance number, a message would play telling you how much more you needed to insert.

There were no digital controls to this - no modern networking. The primitive "computers" were more like equipment you'd see in a science class. So, to deal with the transaction details, the coin slot mechanism would detect the type of coin inserted, mute the microphone on the handset, and transmit a series of tones. Just voltage spikes. The muting prevented the background noise from interfering with the signal detection. Drop a quarter in the slot and you'd hear the background noise suddenly disappear followed by some tapping sounds (this was just bleed through).

It's also relevant to know that cereals used to include a cheap, little toy inside. At one point, Cap'n Crunch had a whistle which had a pitch of 2600Hz.

The story goes that someone* figured out that the tones sent by the payphones were at 2600Hz - same as the whistle. You could pick up a payphone handset and puff into the whistle a certain number of times, and ti would be detected as control signals (inserting money).

That's right! Free phone calls to anywhere. I'm hazy on the specifics, but I'm pretty sure there were other tricks you could do, like directly calling restricted technician numbers, too. The reason the 2600Hz tone was special had to do with something like it was used as a general signal that didn't trigger billing.

It knocked the idea of phone hacking, or "phreaking", from a little known quirk, to an entire movement. Some of the stuff was wild and if you're interested, look up the different "boxes" that people distributed blueprints for. Eventually, the phone companies caught on and started making it harder to get at wires and more sophisticated coin receptacles.

If you've ever seen the magazine 2600 back in the 90s and early 00s, that's the origin of the name.

All that is to say, if you knew nothing about technology and watched a guy whistle into a phone to get special access, you'd probably be freaked out. Who knows what that maniac could do with a flute!

• I could have sworn it was Mitnick, but might have been someone else.