Dual-tone multi-frequency signaling (DTMF) is a telecommunication signaling system using the voice-frequency band over telephone lines between telephone equipment and other communications devices and switching centers. DTMF was first developed in the Bell System in the United States, and became known under the trademark Touch-Tone for use in push-button telephones supplied to telephone customers, starting in 1963. DTMF is standardized as ITU-T Recommendation Q.23. It is also known in the UK as MF4.
In digital imaging, a pixel, pel, or picture element is the smallest addressable element in a raster image, or the smallest addressable element in a dot matrix display device. In most digital display devices, pixels are the smallest element that can be manipulated through software.
Phreaking is a slang term coined to describe the activity of a culture of people who study, experiment with, or explore telecommunication systems, such as equipment and systems connected to public telephone networks. The term phreak is a sensational spelling of the word freak with the ph- from phone, and may also refer to the use of various audio frequencies to manipulate a phone system. Phreak, phreaker, or phone phreak are names used for and by individuals who participate in phreaking.
A red box is a phreaking device that generates tones to simulate inserting coins in pay phones, thus fooling the system into completing free calls. In the United States, a nickel is represented by one tone, a dime by two, and a quarter by a set of five. Any device capable of playing back recorded sounds can potentially be used as a red box. Commonly used devices include modified Radio Shack tone dialers, personal MP3 players, and audio-recording greeting cards.
Plain Old Telephone Service (POTS), or Plain Ordinary Telephone System, is a retronym for voice-grade telephone service employing analog signal transmission over copper loops. Originally POTS stood for Post Office Telephone Service as early phone lines in most parts of the world were operated directly by the local Post Office.
A blue box is an electronic device that produces tones used to generate the in-band signaling tones formerly used within the North American long-distance telephone network to send line status and called number information over voice circuits. During that period, charges associated with long-distance calling were commonplace and could be significant, depending on the time, duration and destination of the call. A blue box device allowed for circumventing these charges by enabling an illicit user, referred to as a "phreaker" to place long-distance calls, without using the network's user facilities, that would be billed to another number or dismissed entirely by the telecom company's billing system as an incomplete call. A number of similar "color boxes" were also created to control other aspects of the phone network.
John Thomas Draper, also known as Captain Crunch, Crunch, or Crunchman, is an American computer programmer and former phone phreak. He is a widely known figure within the computer programming world and the hacker and security community, and generally lives a nomadic lifestyle.
Black boxes were devices which, when attached to home phones, allowed all incoming calls to be received without charge to the caller.
A telephone call or telephone conversation, also known as a phone call or voice call, is a connection over a telephone network between the called party and the calling party. Telephone calls started in the late 19th century. As technology has improved, a majority of telephone calls are made over a cellular network through mobile phones or over the internet with Voice over IP. Telephone calls are typically used for real-time conversation between two or more parties, especially when the parties cannot meet in person.
In telephony, multi-frequency signaling (MF) is a type of signaling that was introduced by the Bell System after World War II. It uses a combination of audible tones for address transport and supervision signaling on trunk lines between central offices. The signaling is sent in-band over the same channel as the bearer channel used for voice traffic.
In telecommunications, in-band signaling is the sending of control information within the same band or channel used for data such as voice or video. This is in contrast to out-of-band signaling which is sent over a different channel, or even over a separate network. In-band signals may often be heard by telephony participants, while out-of-band signals are inaccessible to the user. The term is also used more generally, for example of computer data files that include both literal data, and metadata and/or instructions for how to process the literal data.
Phone fraud, or more generally communications fraud, is the use of telecommunications products or services with the intention of illegally acquiring money from, or failing to pay, a telecommunication company or its customers.
Joybubbles, born Josef Carl Engressia Jr. in Richmond, Virginia, was an early phone phreak. Born blind, he became interested in telephones at age four. He had absolute pitch, and was able to whistle 2600 hertz into a telephone, an operator tone also used by blue box phreaking devices. Joybubbles said that he had an IQ of "172 or something". Joybubbles died at his Minneapolis home on August 8, 2007 (aged 58). According to his death certificate, he died of natural causes with congestive heart failure as a contributing condition.
A clear box is an amplifier used by phreaks to use post-pay pay phones without paying. In some locations, especially rural areas in the United States and Canada, pay phones were configured for "post-pay" operation. In this mode, the handset microphone is muted until payment is made. The user of a post-pay pay phone would dial first, wait until the called party answered, and at that point the user would be prompted to insert the coins. Upon receiving the correct payment for the call, the pay phone would then connect the microphone and allow the caller to speak. An artifact of this scheme was that the called party usually heard the ACTS tones produced by the pay phone upon coin deposit.
The Western Electric model 500 telephone series was the standard domestic desk telephone set issued by the Bell System in North America from 1950 through the 1984 Bell System divestiture. The successor to the model 302 telephone, the model 500's modular construction compared to previous types simplified manufacture and repair and facilitated a large number of variants with added features. Touch-tone service was introduced to residential customers in 1963 with the model 1500 telephone, which had a push-button pad for the ten digits. The model 2500 telephone, introduced in 1968, added the * (asterisk) and # (pound) keys.
The vermilion box is a hypothetical portable improvised line emulator.
A loop line or loop around is a telephone company test circuit. The circuit has two associated phone numbers. When one side of the loop is called, the caller receives a test tone of approximately 1000 Hz. When the second number is called, it produces dead silence, but the party on side A hears the milliwatt test tone drop, and is connected to the person on side B. The purpose of the loop around test is to allow circuit testing to a distant central office without needing a person at the far end. The technician can send a tone down either line and measure the response tone on the second line to determine the path loss parameters.
In Phreaking, the green box was a device whose function was to manipulate the coin collection mechanism of payphones. It employed three of the MF (multi-frequency) tones used in the blue box and could be viewed as a subset of that device.
Ringing is a telecommunication signal that causes a bell or other device to alert a telephone subscriber to an incoming telephone call. Historically, this entailed sending a high-voltage alternating current over the telephone line to a customer station which contained an electromagnetic bell. It is therefore also commonly referred to as power ringing, to distinguish it from another signal, audible ringing, or ringing tone, which is sent to the originating caller to indicate that the destination telephone is in fact ringing.
Matthew Weigman is a blind American man who has used his heightened hearing ability to help him deceive telephone operators and fake various in-band phone signals. Before his arrest at the age of 18, Weigman had used this ability to become a well known phone phreaker, memorizing phone numbers by tone and performing uncanny imitations of various phone line operators to perform pranks such as swatting on his rivals.
