The two dug through the reference books and before long they struck pay dirt: an international telephone technical standard that listed the MF frequencies. "I froze and grabbed Steve and nearly screamed in excitement that I'd found it. We both stared at the list, rushing with adrenaline. We kept saying things like 'Oh, shit!' and 'Wow, this thing is for real!' I was practically shaking, with goose bumps and everything. It was such a Eureka moment. We couldn't stop talking all the way home. We were so excited. We knew we could build this thing. We now had the formula we needed! And definitely that article was for real." Jobs agrees: "We kept saying to ourselves, 'It's real. Holy shit, it's real.'"

That very day Wozniak and Jobs purchased analog tone generator kits from a local electronics store; this was the Silicon Valley in 1971, after all, and such things were easily available. Later that night they had managed to record pairs of tones on cassette tape, enough to make a blue box call. But it didn't quite work. They were able to disconnect a call to 555-1212 with 2,600 Hz--they heard the kerchink! of the trunk--but their MF tone tape recordings didn't do anything. They worked late into the night trying to figure out what was wrong. In the end Wozniak concluded that the tone generator just wasn't good enough to make the telephone network dance to his tunes.

Wozniak started classes at Berkeley the next day. But he couldn't get his mind off of blue boxes and phone phreaking.

He thought more about the analog blue box that he and Jobs had tried to build. The problem with analog circuits is that they are imprecise. This is because the components they are constructed with--resistors and capacitors and inductors and such--are themselves inexact. For example, if you want an analog circuit to generate a tone at a particular frequency, as you would for a blue box, you might need a resistor of 1000 ohms and a capacitor of 0.1 microfarads. Unfortunately, when you buy a resistor, you can't get one that is exactly 1000 ohms; rather, it is guaranteed to be only within 10 percent of that value. If you want to spend more money, you can get ones that are more accurate--ones whose values vary by only 5 percent or even 1 percent--but there is always some inaccuracy in the individual components. When you combine them to build a circuit the inaccuracies often compound. Worse, the component values vary with temperature. So you might spend time tuning your blue box in the warmth of your dorm room and get it all working and then go out to a pay phone in the cold night air only to find that it doesn't work anymore.

Steve Wozniak had been designing electrical circuits for years; just a year earlier he had designed his own tiny computer, the "Cream Soda Computer," so named because he and a friend drank tons of cream soda while they were building it. Computers are made out of digital circuits, circuits that deal with 1s and 0s rather than the full range of values that analog circuits can handle. While this may seem like a limitation, it gives digital circuits a huge advantage. Digital circuits are exact and their building block components don't vary from one to another, nor do they vary with temperature. With this in mind Wozniak started thinking about how to build a digital blue box, which would be made up of the chips used to build computers, not analog components such as resistors and capacitors and transistor oscillators. It would use a quartz crystal, like those used in the then newfangled digital watches, for ultimate accuracy and rock-solid stability.