In the early 1970’s I heard that if you sent the right tones, you could dial people’s phone numbers without incurring a charge.
I got on the phone and did my best verbal immatation of a tonal dial. I actually did a phone call. It was some stranger, but WTF.
Did anybody else try this or hear of it. The phones of the day were rotory.
You can go to Cap’n Crunch’s homepage and read all about it. He discovered that the whistle that came with Cap’n Crunch cereal was the right frequency to allow him to make long distance calls. He can explain it far better than I.
Thanks beatle.
Anybody else actually do this. I was about ten when I tried this once.
It’s called phreaking, and no, I’ve never done it.
It used to be quite common, because the telephone switches used tones to control operation. I believe that this one was the infamous “blue box”, though I could definitely be wrong about that, there were all sorts of colors.
The correct tone was 2600hz, (ever wondered about alt.2600.*?). Phone systems have since been upgraded, and this technique will generally not work, and may get you arrested/fined.
There are actually a series of tones that can be played into a phone to represent different coins/monetary increments. This only works on some proprietary phone networks now. The audio tones are similar to the tones used for dialing and can be played from a tape recorder, digital device or any other method like voice or whistle(even though I am skeptical about the voice though.) I have got modems to respond to my voice, but dialing a whole number seems a bit far out to me. BTW, phreaking encompasses a lot more than tone reproduction. Phreaking focuses more on hardware and manipulation of major line controllers like PBX systems. And it was called the “Blue Box” TheNerd, able to produce 2600Mhz tone. My favorite phreaking folklore was the “Blotto Box” supposedly able to take out phone networks for miles around 
Dunno if anyone ever did that or if it was just an UL. Anyone know?
“Teaching without words and work without doing are understood by very few.”
-Tao Te Ching
It was thirty years ago, and I don’t expect it would work any more.