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line at their disposal could open many more possibilities than just free phone calls: they could dial into phone company test switches, to long-distance route operators and into conference lines — which meant they could set up their phreaker conference calls. Quite simply, possession of a blue box gave the user the same control and access as a Bell operator. When operator-controlled dialling to Europe was introduced in 1963, phreakers with MF-ers found they could direct-dial across the Atlantic, something ordinary subscribers couldn’t do until 1970.

The only real flaw with blue boxes was that Bell Telephone’s accounts department could become suspicious of subscribers who seemed to spend a lot of time connected to the 1-800 numbers of, say, Holiday Inn or the Army Recruiting Office, or talking for hours to an out-of-area directory enquiries number. The phone company might then monitor the line. Phreaking, after all, was theft of service and phreakers could be prosecuted under various state and federal laws.

To get around this, canny phreakers began to use public phone booths, preferably isolated ones. The phone company could hardly monitor every public call box in the United States; and even when the accounts department realized that a particular pay phone had been used suspiciously, the phreaker would have long since disappeared.

By the late 1960s blue boxes had become smaller, more portable. The bulky vacuum tubes mounted on a metal chassis had been replaced by transistors in slim boxes only as large as their keypads. Some were built to look like cigarette packs or transistor radios. Cleverer ones — probably used by drug dealers or bookies — were actually working transistor radios that concealed within their wiring the components of an operational blue box.

What made Bell’s technology particularly vulnerable was that almost anything musical could be used to reproduce the tone frequencies. Musical instruments like flutes or horns or organs could be made to recreate Bell’s notes. Then they could be taped, and a simple cassette player could work as a primitive MF device. One of the easiest ways to make a free call was to record the tones for a desired number in the correct sequence on to a cassette tape, go to a phone

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