How could a whistle get free phone calls? Old telephone routing equipment worked on sound at a specific frequency. Some whistles blew at exactly the same frequency and could be used to trick the phone equipment. The people who were cheating the phone system called themselves “phreaks”, which was a combination of “phone” and “freak”. Several people who became big names in the computing industry started out as phreaks. They were able to do it because of the way early phones worked.
The invention of the telephone is credited to Alexander Graham Bell, but he was not necessarily the first person to invent it. He was the first person to patent it. There is a lot of controversy over who actually invented the telephone, but all of the people involved were building on numerous inventions that came over the century before them. As with all inventions, everybody took technology that had been developed and added to it or improved on it or changed its usage. Whoever invented it, the first telephone line and the first telephone exchange was constructed in 1877. There didn’t seem much need for one at first, but the telephone was one of those inventions that every body needs. By 1881, there were 50,000 telephones in the US alone. By 1900 there were 600,000 and by 1910 there were 6 million.
The first phones didn’t have a dial. You lifted the speaker part, were connected to an operator, and asked for the number that you wanted. The operator would connect you. The first phone with a dial was invented in 1891 by an undertaker called Almon Brown Strowger. He believed that the local operator was sending all undertaking business to one of his competitors, so he came up with a way to automate the phone exchanges, and that called for a way to dial the number from the phone. His idea was the rotary dial. If you are as old as me, you remember rotary phones. You put your finger in the whole next to the number and spin the dial all the way round before releasing it. The dial moved back to its starting place and you could dial the next number. These rotary dial phones worked on a system similar to that of Morse Code. Each number and symbol on the phone had a corresponding number of pulses of electricity. For example, 6 might be 6 pulses (which would make sense). When you dial 6, a switch in the phone would cut the electric signal rapidly to create six pulses of electricity. The problem with these systems was that the signals couldn’t be sent very far because of electrical distortion in the cables. That meant relay stations were necessary to redo the pulses.
The phone companies were looking for an alternative and they came up with sound. The idea was similar to the rotary dial, except the clicks were replaced with a sound frequency. The frequency for one would be different to two, and so on. Sound could travel further, and they could be amplified easily. Sound can also be transmitted over radio waves and microwaves. The phone companies had several different sound frequencies programmed into their phones. They had the numbers, the letters, the symbols, and anything else that a phone would need to do. However, they also had frequencies that were only used by the phone companies.
We are so used to free international Internet phone calls these days that it is easy to forget that phoning someone used to be very expensive. Phoning in the same city could be expensive, but international calls could cost several dollars a minute. And this is where phone phreaks came in. Back with the rotary phones, they had worked out that there were some sequences of pulses that the phone companies used to leave a line open so they could contact their company. The phreaks learned that if they could replicate those pulses, they could get free phone calls. They could do this by pressing the switch hook, which is the metal cradle that the phone sits on to hang it up, very quickly to emulate the pulses. When the new tone dial phones were introduced, this didn’t work. However, in 1957, a blind seven-year old boy with perfect pitch realized that if he whistled the fourth E above middle C, which is 2637 Hz, he could cut the phone off. Other phreaks learned about this and they tried different frequencies. It turned out that a frequency of 2600 Hz would reset the line, leaving it open. They could then use short groups of whistles to dial a number, getting free phone calls to anywhere they wanted. It got amusing when they discovered that a free child’s whistle given out in boxes of Cap’n Crunch breakfast cereal played a note at exactly 2600 Hz. The phreaks could use that whistle to easily get free phone calls.
Many of these phreaks were more interested in how the phone system worked than in the free phone calls they could get. They loved learning about the technology and finding ways to game it. This knowledge and fascination would bring many of them to work in the burgeoning computer industry. And this is what I learned today.
Sources
https://en.wikipedia.org/wiki/DTMF_signaling
https://en.wikipedia.org/wiki/Phreaking
https://en.wikipedia.org/wiki/History_of_the_telephone
Photo by Nic Wood: https://www.pexels.com/photo/vintage-british-telecom-telephone-cream-28248427/