Yes believe it or not, I built a blue box in 1973, and a red box at the same time. Both worked.
The red box, a/k/a a "Dimetron" emulated the sound of coins going into a payphone. Most of these hacking deals were simply eliminated by installing filters.
This all came crashing down when a certain friend of mine, who wisely kept me at arm's length, broke into a major state university's phone system (physically) with the purpose of installing some equipment on the outgoing phone lines. Ah, those were the days. He went to jail. Nobody came knocking. I was in a distant outer circle.
Before those dark days, we called phone booths in London, sent calls from one phone to the next going across the globe first. We could choose satellite transmission, or ocean cable. All that you read on the subject, while seemingly unbelievable, was true.
For those interested,
http://www.lospadres.info/thorg/lbb.html that's the seminal article from 1971 on the subject.
More recently,
http://www.amazon.com/Phil-Lapsley/e/B00BBNTTIY?tag=duckduckgo-osx-20 that's the book "Exploding the phone" by Phil Lapsley.
Very interesting stuff.
