2600 Hz is the frequency in hertz (cycles per second) that AT&T formerly put as a steady signal on any long-distance telephone line that was not currently in use. Prior to widespread use of out-of-band signaling, AT&T used in-band signaling, meaning that signals about telephone connections were transmitted on the same line as the voice conversations. Since no signal at all on a line could indicate a pause in a voice conversation, some other way was needed for the switch to determine which circuits were available. This was accomplished by placing 2600Hz on idle trunks, and removing it when a call was ready to use the circuit. FreQuency is a music video game developed by Harmonix and published by SCEI. It was released in November 2001. ... The hertz (symbol: Hz) is the SI unit of frequency. ... AT&T (NYSE: T) is the largest provider of both local and long distance telephone services, wireless service under the brand Cingular Wireless, and DSL Internet access in the United States. ... In telecommunication, signalling (or signaling) has the following meanings: The use of signals for controlling communications. ... Long distance in telecommunications, refers to telephone calls made outside a certain area, usually characterized by an area code outside of a local call area. ... A telephone line (or just line) is a single-user circuit on a telephone communications system. ... In telecommunications, the term out-of-band signaling has the following meanings: 1. ... It has been suggested that this article or section be merged with In-band signalling. ... For the movie from Francis Ford Coppola, see The Conversation. ... A Verizon Central Office in Lakeland, Florida at night. ...

Knowing this, certain people developed a way to use a whistle or other device (i.e. a blue box) to generate a 2600-hertz tone on a line that was already in use, indicating to the far end switch that the line was idle again. When the tone stopped, the switch assumed another call was being set up, and listened for dialed digits indicating how to connect the call. Interoffice signalling was accomplished using CCITT MF digits, not the DTMF which was introduced later for subscriber use under the name "touch-tone". A whistle is a one-note woodwind instrument which produces sound from a stream of forced air. ... The blue box previously owned by Steve Wozniak, on display at the Computer History Museum. ... Pitch is the perceived fundamental frequency of a sound. ... ITU-T is the telecom standardization organization of the International Telecommunication Union (ITU). ... Dual-tone multi-frequency (DTMF), also known as Touch Tone® is used for telephone signaling over the line in the voice frequency band to the call switching center. ...

In order for blue boxing to work, the initial call must be made across an interoffice MF trunk, so local calls (those which originated and terminated on the same switch) wouldn't work. By placing a call to a distant toll-free number, interoffice trunks could be involved but no billing was incurred. Using a blue box during a toll-free call would allow the user to call anywhere for free. However, due to modifications in the phone systems, Blue Boxing rarely works today, with the exception of some third-world or technologically impaired countries. Cracking the phone system became a hobby for some who came to be known as phone phreaks. The blue box previously owned by Steve Wozniak, on display at the Computer History Museum. ... A toll-free telephone number (or Freephone number in the UK) is a special telephone number, in which the calling party is not charged for the call by the telephone operator. ... Phreaking is a slang term coined to describe the activity of a subculture of people who study, experiment with, or explore telephone systems, the equipment of telephone companies, and systems connected to public telephone networks. ...

At one point in the 1960s, packets of the Cap'n Crunch breakfast cereal included a free premium: a small whistle that (by coincidence) generated a 2600 hertz tone. By dialing a telephone number, covering one of the whistle's two holes, and then blowing the whistle, it could fool the phone company into thinking the line was not being used while, in fact, the user was now free to make a call to any destination in the world. The phreaker Captain Crunch adopted his nickname from this whistle. 2600: The Hacker Quarterly got its name from the frequency itself. The 1960s decade refers to the years from January 1, 1960 to December 31, 1969, inclusive. ... For information on the phone phreak called Captain Crunch, see John Draper. ... This article does not adequately cite its references or sources. ... Look up premium in Wiktionary, the free dictionary A Premium may refer to: Premium rate telephone number, the UK Premium Bond Premium outlet Risk premium, in finance, the monetary difference between the guaranteed return and the possible return on an investment This is a disambiguation page — a navigational aid which... A telephone number is a sequence of decimal digits that uniquely indicates the network termination point. ... Phreaking is a slang term for the action of making a telephone system do something that it normally should not allow—in the words of one former practitioner, making the phone company bend over and grab its ankles. Sometimes, phreaking will be considered illegal, like in the act of... John T. Draper (born 1944), also known as Captain Crunch, Crunch or Crunchman (after Capn Crunch, the mascot of a breakfast cereal), was a phone phreak. ... // A nickname is a short, clever, cute, derogatory, or otherwise substitute name for a person or things real name (for example, Bob, Rob, Robby, Robbie, Robi, Robin, Bobby, Rab, Rabbie, Bert, Bertie, Butch, Bobbers, Bobert, Beto, Bobadito, and Robban (in Sweden), are all nicknames for Robert). ... Fall 2004 (21:3) 2600 Issue 2600: The Hacker Quarterly is a traditional (printed) magazine named for the fact that phreakers in the 1960s found that the transmission of a 2600 Hertz tone (which could be produced perfectly with a plastic toy whistle given away free with Capn Crunch...

Today, long-distance companies use Signalling System 7, which puts all channel signals on a separate signaling channel, making it more difficult to break into the phone system. Signalling System #7 (SS7) is a set of telephony signalling protocols which are used to set up the vast majority of the worlds PSTN telephone calls. ... Channel, in communications (sometimes called communications channel), refers to the medium used to convey information from a sender (or transmitter) to a receiver. ...

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