Blue box

In September 1971, Stephen Wozniak , who had already studied at the university for a long time, caught the eye of an article in the Esquire magazine. It described some “telephone freaks” who learned how to crack phone codes and make free calls around the world ^[3] . Wozniak became very interested in this topic and immediately called Steve Jobs . Having carefully studied the article, they came to the conclusion that everything described is similar to the truth ^[4] . The telephone line was captured using sound simulation of a tone signal of a certain frequency. Then it was necessary to dial the number, also through imitation of a call in tone mode. As it turned out, there was a whole subculture of phreakers involved in hacking telephone networks. One of them, for example, possessing absolute hearing and voice, could make a sound of the right frequency without any additional devices ^[5] . Another, hiding under the pseudonym Captain Crunch , discovered that the whistle , which manufacturers put in packages of the same name with oatmeal (“Cap'n Crunch”), can make a sound of the right tone suitable for capturing the line. For subsequent dialing, Crunch used a home-made device called the “Blue box” (“blue box”). Wozniak and Jobs set about trying to make such a “box” ^[6] . Wozniak had a good idea of ​​how it should be arranged, but the first analog prototype made by him turned out to be imperfect and did not produce reliable tone signals ^[7] . Then Wozniak made a fully digital device that reproduced frequencies with the necessary accuracy. The device worked, and in the future, Steve Wozniak said that he had never invented anything more witty and innovative than this digital “blue box” ^[8] .

At first, friends had fun, calling in different parts of the world and arranging pranks. Once Wozniak phoned the Vatican and, introducing himself as Henry Kissinger , asked Pap for the phone ^[9] . Soon, Jobs realized the commercial potential of their invention ^[10] . They organized handicraft production and successful sales of “blue boxes” among students and local residents, although this business was illegal and quite risky. At first, making one “box” cost Wozniak about $ 80, but then he made a printed circuit board that made it possible to produce 10-20 “boxes” at once, and the cost of one piece dropped to $ 40. Friends sold ready-made “boxes” for $ 150 apiece, sharing income equally ^[11] . In total, they did and managed to sell about a hundred “boxes” and made good money. The business, it was decided to stop, as too risky, after another potential buyer, threatening with a gun, took the device from them and disappeared ^[12] . Probably, the story with the “blue boxes” convinced Jobs that electronics can not only bring joy, but also bring good income ^[13] . The same story laid down the principles of their future cooperation: Wozniak creates another ingenious invention for the benefit of mankind, and Jobs comes up with how to best design and present it in the market in order to make good money ^[14] .

The blue box used the U.S. telephone feature of the 1970s. The user first dials a telephone number served by another exchange . The call goes through the "home" PBX and the "external" PBX. When the call is ringing, the user uses the Blue box to send a tone with a frequency of 2600 Hz (or 2600 Hz and 2400 Hz for international calls). This signal is supervisory, simulating the state of the trunk in the end state on the initiative of the calling subscriber (“the subscriber hung up”). By sending such a signal, the user informs the "external" PBX that the conversation is over and the line is free. However, the home PBX ignores this signal, believing that the line is still busy for a call.

After a signal of 2600 Hz, the line is reset ( supervision flash ), after which the user can use Blue Box to dial either a new telephone number or one of the numerous telephone company extensions preceded by a KP ( key pulse ) tone signal. After completing the dialing and two-tone signal ST ( start ), the PBX considers that the user is still using the old line, but in fact the user is calling a completely different number. There are two types of KP - KP1 (used mainly for calls within the network) and KP2 (for international calls).

The exchange will register only the part of the request preceding the 2600 Hz signal. Thus, the user could make long-distance or international calls for free or for a significantly lower fee.

There were also techniques for making transit calls through the PBX of the originally called subscriber.

• Engression, Joseph

• Wozniak C. , Smith D. Steve Jobs and I. The True Story of Apple = iWoz. - M .: Eksmo , 2011 .-- 288 p. - ISBN 978-5-699-53452-4 .
• Isaacson W. Steve Jobs = Steve Jobs: A Biography. - M .: Astrel , 2012 .-- 688 p. - ISBN 978-5-271-39378-5 .