The 1971 article about phone hacking that inspired Steve Jobs.

In 1971, Slate columnist Ron Rosenbaum wrote an article for Esquire about a loose confederation of proto-hackers who built devices—little blue boxes—that could crack phone networks. According the New York Times obituary of Apple founder Steve Jobs, after reading Rosenbaum’s article, Jobs and his partner in founding Apple, Steve Wozniak, “collaborated on building and selling blue boxes, devices that were widely used for making free—and illegal—phone calls. They raised a total of $6,000 from the effort.” The original 1971 article, “Secrets of the Little Blue Box,” is reprinted below, with permission from the author. It’s also available in Rosenbaum’s collection The Secret Parts of Fortune. Also in Slate: Rosenbaum reflects on the article that inspired Steve Jobs.

In Which We Explore the Web of the Original Hackers

There is an underground telephone network in this country. Al Gilbertson (I’ve changed his name) discovered it the day after his arrest for manufacturing illegal “blue boxes.” A crime he is not exactly repentant about. I am sitting in the living room of the creator of the blue box. Gilbertson is holding one of his shiny black-and-silver blue boxes comfortably in the palm of his hand, pointing out the thirteen little red push buttons sticking up from the console. He is dancing his fingers over the buttons, tapping out discordant beeping electronic jingles. He is trying to explain to me how his little blue box does nothing less than place the entire telephone system of the world, satellites, cables and all, at the service of the blue-box operator, free of charge.

“Essentially it gives you the power of a super operator. You seize a tandem with this top button," he presses the top button with his index finger and the blue box emits a high-pitched cheep,  "and like that" — cheep goes the blue box again — "you control the phone company's long-distance switching systems from your cute little Princess phone or any old pay phone. And you've got anonymity. An operator has to operate from a definite location: The phone company knows where she is and what she's doing. But with your beeper box, once you hop onto a trunk, say from a Holiday Inn 800 number, they don't know where you are, or where you're coming from, they don't know how you slipped into their lines and popped up in that 800 number. They don't even know anything illegal is going on. And you can obscure your origins through as many levels as you like. You can call next door by way of White Plains, then over to Liverpool by cable, and then back here by satellite. You can call yourself from one pay phone all the way around the world to a pay phone next to you. And you get your dime back too."

"And they can't trace the calls? They can't charge you?"

"Not if you do it the right way. But you'll find that the free-call thing isn't really as exciting at first as the feeling of power you get from having one of these babies in your hand. I've watched people when they first get hold of one of these things and start using it, and discover they can make connections, set up crisscross and zigzag switching patterns back and forth across the world. They hardly talk to the people they finally reach. They say hello and start thinking of what kind of call to make next. They go a little crazy." He looks down at the neat little package in his palm. His fingers are still dancing, tapping out beeper patterns.

"I think it's something to do with how small my models are. There are lots of blue boxes around, but mine are the smallest and most sophisticated electronically. I wish I could show you the prototype we made for our big syndicate order."

He sighs. "We had this order for a thousand beeper boxes from a syndicate front man in Las Vegas. They use them to place bets coast to coast, keep lines open for hours, all of which can get expensive if you have to pay. The deal was a thousand blue boxes for $300 apiece. Before then we retailed them for $1,500 apiece, but $300,000 in one lump was hard to turn down. We had a manufacturing deal worked out in the Philippines. Everything ready to go. Anyway, the model I had ready for limited mass production was small enough to fit inside a flip-top Marlboro box. It had flush touch panels for a keyboard, rather than these unsightly buttons sticking out. Looked just like a tiny portable radio. In fact, I had designed it with a tiny transistor receiver to get one AM channel so in case the law became suspicious the owner could switch on the radio part, start snapping his fingers, and no one could tell anything illegal was going on. I thought of everything for this model — I had it lined with a band of thermite which could be ignited by radio signal from a tiny button transmitter on your belt, so it could be burned to ashes instantly in case of a bust. It was beautiful. A beautiful little machine. You should have seen the faces on these syndicate guys when they came back after trying it out. They'd hold it in their palm like they never wanted to let it go, and they'd say, 'I can't believe it. I can't believe it.' You probably won't believe it until you try it."

You Can Call Long Distance for Less Than You Think

"You see, a few years ago the phone company made one big mistake," Gilbertson explains two days later in his apartment. "They were careless enough to let some technical journal publish the actual frequencies used to create all their multi-frequency tones. Just a theoretical article some Bell Telephone Laboratories engineer was doing about switching theory, and he listed the tones in passing. At ----- [a well-known technical school] I had been fooling around with phones for several years before I came across a copy of the journal in the engineering library. I ran back to the lab and it took maybe twelve hours from the time I saw that article to put together the first working blue box. It was bigger and clumsier than this little baby, but it worked."

It's all there on public record in that technical journal written mainly by Bell Lab people for other telephone engineers. Or at least it was public. "Just try and get a copy of that issue at some engineering-school library now. Bell has had them all red-tagged and withdrawn from circulation," Gilbertson tells me.

"But it's too late. It's all public now. And once they became public the technology needed to create your own beeper device is within the range of any twelve-year-old kid, any twelve-year-old blind kid, as a matter of fact. And he can do it in less than the twelve hours it took us. Blind kids do it all the time. They can't build anything as precise and compact as my beeper box, but theirs can do anything mine can do."

"How?"

"Okay. About twenty years ago AT&T made a multibillion-dollar decision to operate its entire long-distance switching system on twelve electronically generated combinations of six master tones. Those are the tones you sometimes hear in the background after you've dialed a long-distance number. They decided to use some very simple tones — the tone for each number is just two fixed single-frequency tones played simultaneously to create a certain beat frequency. Like 1300 cycles per second and 900 cycles per second played together give you the tone for digit 5. Now, what some of these phone phreaks have done is get themselves access to an electric organ. Any cheap family home-entertainment organ. Since the frequencies are public knowledge now — one blind phone phreak has even had them recorded in one of those talking books for the blind — they just have to find the musical notes on the organ which correspond to the phone tones. Then they tape them. For instance, to get Ma Bell's tone for the number 1, you press down organ keys F⁵ and A⁵ [900 and 700 cycles per second] at the same time. To produce the tone for 2 it's F⁵ and C⁶ [1100 and 700 cps]. The phone phreaks circulate the whole list of notes so there's no trial and error anymore."

He shows me a list of the rest of the phone numbers and the two electric organ keys that produce them.

"Actually, you have to record these notes at 3¾ inches-per-second tape speed and double it to 7½ inches-per-second when you play them back, to get the proper tones," he adds.

"So once you have all the tones recorded, how do you plug them into the phone system?"

"Well, they take their organ and their cassette recorder, and start banging out entire phone numbers in tones on the organ, including country codes, routing instructions, 'KP' and 'Start' tones. Or, if they don't have an organ, someone in the phone-phreak network sends them a cassette with all the tones recorded, with a voice saying 'Number one,' then you have the tone, 'Number two,' then the tone, and so on. So with two cassette recorders they can put together a series of phone numbers by switching back and forth from number to number. Any idiot in the country with a cheap cassette recorder can make all the free calls he wants."

"You mean you just hold the cassette recorder up the mouthpiece and switch in a series of beeps you've recorded? The phone thinks that anything that makes these tones must be its own equipment?"

"Right. As long as you get the frequency within thirty cycles per second of the phone company's tones, the phone equipment thinks it hears its own voice talking to it. The original granddaddy phone phreak was this blind kid with perfect pitch, Joe Engressia, who used to whistle into the phone. An operator could tell the difference between his whistle and the phone company's electronic tone generator, but the phone company's switching circuit can't tell them apart. The bigger the phone company gets and the further away from human operators it gets, the more vulnerable it becomes to all sorts of phone phreaking."

"What about the recent series of blue-box arrests all across the country — New York, Cleveland, and so on?" I asked. "How were they caught so easily?"