Blue Box

January 3, 2018

Question from E-mail

How did you make the blue box? Do you still own one? Also.. Do you have the Apple I still or any screen shots of it and programs? If so send me some. Thanks, Andy age:12


I read an article in Esquire Magazine. It was about the October edition in 1971. The article was entitled “Secrets of the Blue Box–fiction” by Ron Rosenblum. Halfway through the article I had to call my best friend, Steve Jobs, and read parts of this long article to him. It was about secret engineers that had special equipment in vans that could tap into phone cables and redirect the phone networks of the world. The article had blind phone phreaks like Joe Engessia Jr. of Nashville, and the hero of them all, Captain Crunch. It was a science fiction world but was told in a very real way. Too real a way. I stopped and told Steve that it sounded real, not like fiction. They gave too many engineering details and talked on too real a way to have been made up. They even gave out some of the frequencies that the blue box used to take control of the international phone network.

The next day was Sunday. Steve and I drove to SLAC (Stanford Linear Accelerator Center, the same place the Homebrew Computer Club would meet 4 years later) because they always left a door or two unlocked and nobody thought anything about a couple of strangers reading books and magazines in their technical library. Finally we found a book that had the exact same frequencies that had been mentioned in the Esquire article. Now we had the complete list.

We went back to Steve’s house and built two, somewhat unstable, multivabrator oscillators. We could see the instability on a frequency counter, but we were in a hurry. We would set one oscillator to 700 Hz and the other to 900 Hz (for a “1”) and record it on a tape recorder. Then we’d adjust the oscillators and record the next digit, and so on. But it wasn’t good enough to make a call as in the article. So we tried one oscillator at a time. It still wasn’t good enough. I was off to Berkeley the next day so it would be some weeks before I designed a digital blue box that never missed a note. The key to debugging it was a guy in the dorm, Mike Joseph, that had perfect pitch. If it didn’t work, he’d tell me what notes he heard. If one of them was a C-sharp and was supposed to be an A, I could look up the C-sharp frequency and find out where my frequency divider was off, and replace a diode that was bad. All my problems were diodes that I bought at Radio Shack in a bag where some might actually work.

The key to the phone network then was a high E note, two octaves above the high E string on a guitar. It was 2600 Hz. The Captain Crunch cerial whistle could blow this note and seize a phone line. The blue box then took over with it’s dual frequency combinations known as ‘multfrequency’ or MF, similar to touch tone frequencies but not the same. Some phone systems worked on SF, or Single Frequency. The 2600 Hz Captain Crunch whistle could make the entire call. One long whistle to seize the line, a short one for a “1”, two short ones for a “2”, etc. The blind phone phreak, Joe Engressia, could dial an entire call just by whistling it out of his own mouth!

If you want to test this principal, play 2600 Hz into and long distance call and you’ll be disconnected. We had fun doing that in the dorms. But don’t be stupid and try to make a blue box today. It’s much easier to make or program, but you’re nearly guaranteed to get caught right away in most places. I experimented with it in 1972 but even then I paid for my own calls. I only used the blue box to see how many things I could do.

I have Apple I’s and original software and things but they’re in storage and I don’t have time to get them out and get them working right now.