Hear how Steve Jobs and Steve Wozniak's BLUE BOX worked and why 2600 is such an iconic number for hacking.

Originally published at: https://boingboing.net/2020/12/01/hear-how-steve-jobs-and-steve-wozniaks-blue-box-worked-and-why-2600-is-such-an-iconic-number-for-hacking.html


I should remember this, from the dying age of Capt. N . Crunch, what are a green box and red box?


Not quite. The 2600Hz tone was sent by both ends of a long-distance trunk line to indicate that it was open and ready for use. It had nothing to do with pay phones.

If you had a long-distance connection open, and generated a 2600Hz tone (I used to whistle it fairly reliably), then the system would drop the connection but remain open for commands. Then, you could use your blue box to generate further instructions (all of them combinations of two tones) to connect a call anywhere in the world, and be billed for only the original call. If you did it with a call to Information or a toll-free number, the call would be free.

And if you called from a pay phone, it would not be traceable on your end.


I used to love the 2600 zine. I admired phreaks and hackers, though I didn’t have sufficient focus, patience and drive to be one myself! I miss my copper-pair landline…


Just in case you all missed out on the chance to own one of Woz’s blue boxes:


Right – it just so happened it was an easy way to get free calls from a payphone.

I remember when I was young and doing hobbyist phreaking projects I was disappointed to find that most payphone exploits had stopped working because payphones would no longer light up the voice coil until money had been inserted and a call initiated. (You could still sometimes work around it with enough dexterity if you could drop the call in a way that your coin was returned by the voice coil wasn’t reset.)


Hey thank you - I regret mentioning pay phones in the audio itself, and will edit the soundfile for this episode with an addendum better matching both of your descriptions. Much appreciated, @smoobly and @ficuswhisperer - a 2600 Hz tweet from a cap’n crunch whistle to you both.


No doubt! - Do you just mean a regular phone landline in itself, or was copper-pair an exploit of some kind? During this pandemic I became interested in establishing a new landline for our home - cell use in our neighborhood has maxed out cell coverage; a problem I don’t recall being present with landlines , leading to dropped calls and other bad service. (I’m sure landlines can have overruse too, with lines tied up, but cells seem much weaker)

It turns out all the local services have moved to VOIP (boo) - or some phone over wifi drag - and even with the existing wiring in the home a separate voltage driven landline is no longer available. Perhaps a landline is still available but at a premium cost. Don’t ditch yours if you have one, anyone.


The other thing about the Blue Box is that it uses a completely different set of dual-tone frequencies from those used by an ordinary touch-tone keypad for the digits 0-9. This was done to prevent people from being able to signal the trunk lines with phones.
The Woz Blue Box was quite advanced for its time, using a crystal oscillator to make these tones, rather than the ICL8038 sine wave generator with a bunch of trim pots that competing units used. Those required initial adjustment and could easily drift off frequency, causing them to be detected by the phone cops.


73 magazine (devoted to ham radio) had a three part article about the phone system in 1975, starting with the April issue. The June issue has schematics and details for red and blue boxes.

Don’t bother trying them, they no longer work (well the circuits work if you build them, but the phone system won’t react to them).
73 got into trouble with Bell for printing that series, which had impact later that year when the magazine launched Byte magazine.

There was a trick to adding 3 buttons to touchtone pads, but after it flowed back into my.memory, it generated some extra tones but had nothing to do with free phone calls.


(sound of an old man’s hideous hacking laugh…) No, copper pair was how they delivered phone service… just two copper wires. Once upon a time, in the 80s, I worked for a telephony engineer, and learned that old land-line phones work on two wires. Phones did have four, to (if I remember) enable a second line on the one instrument. The two wires are called the tip and the ring.


laughs! I didn’t mean to say it was something was obscure, just you mentioned 2600 first and I wondered if you were referring to something they’d written about as a cabling trick. Regards to your work experience, too!

Interesting - I’d never heard that! Tip and Ring are the basis of TRS connections for audio. (Tip Ring Sleeve) - A basic insert cable is a TRS connector that Y’s out into two separate cables, one for Tip and the other for Ring. Usually the TRS is for a stereo signal whereas a mono cable is just TS, Tip and Sleeve. Since telephone wires are monophonic, I’d presume they’d be TS, not TR. Fun to think about.


Strictly speaking, MF (the long-distance signalling tones) preceded DTMF (Touch-Tone) by decades. It was in use in parts of the Bell System long-distance network by the early 1940s. A failed attempt was made in 1948 to use these tones (generated by plucked reeds) for customer signalling. Touch-Tone wouldn’t be deployed until 1963, when transistorized oscillators could be made cheaply and reliably.

There is a fourth column in the DTMF standard, for a total of 16 possible tones. These were used for setting priority on military phone networks, and are used by ham radio operators to control repeaters. I think one of the Evan Doorbell tapes may have mentioned something about them also being used on early conferencing systems. If you have a phone capable of generating them, an Asterisk PBX can recognize them, and you could set up your system to actually use them for whatever you might come up with.


I worked as a communications tech for ATT from 1972 until 2005. I worked on (in) a 4a long distance switch. There was usually one per city. This was pre computer, all electrical xbar switches. When a call was made and a path
established all signaling and voice used the same path. Blue boxes were a major problem. So much so that ATT completely changed the way things worked. They invented and installed “STP” switches. Signal transfer points. There were now two paths, one for signals (answer, hang up, busy, etc) and another for voice. The blue box would no longer work. Of course this was happening at the same time computing was entering the scene. Once all the switches were 2b computers it pretty much made the issue mute. And our 4A xbar switcher that took up two plus floors of a building (Birmingham, Al) went to a couple racks of equipment in the corner of the room. The blue box helped drive this change. Side note. I tested long distance circuits going out to small cities and towns around the state. If we got tired of waiting for the circuit to become idle we would plug a 2600 tone in, knocking down the call. And yes, some of the guys could whistle a 2600 tone. Fun times.


Welcome to BoingBoing and thank you for such an interesting post. I love obscure first-hand knowledge like this.


Re: spoken word about Phreaking: https://www.evan-doorbell.com/


Wow I’d never heard this - What a delight! Thank you @cementimental

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No problem. Strangely relaxing listening :slight_smile:

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I suddenly remember that in Steal this Book there is a bit abiut using the phone for free. Not technical, but it was clearly influenced by phone phreaks.

A few times forty years ago I ended up with copies of the Yippie! Newsletter, and it had some things, though a bit more blatantly illegal, given it wasn’t to explore, but to get free phone calls.

But then that happened generally, people trying to do tricks with the phone system, but others (like people who bought blue boxes) just wanting free phone calls.

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