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.
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.
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. POTS was the standard service offering from telephone companies from 1876 until 1988 in the United States when the Integrated Services Digital Network (ISDN) Basic Rate Interface (BRI) was introduced, followed by cellular telephone systems, and voice over IP (VoIP). POTS remains the basic form of residential and small business service connection to the telephone network in many parts of the world. The term reflects the technology that has been available since the introduction of the public telephone system in the late 19th century, in a form mostly unchanged despite the introduction of Touch-Tone dialing, electronic telephone exchanges and fiber-optic communication into the public switched telephone network (PSTN).
A dial tone is a telephony signal sent by a telephone exchange or private branch exchange (PBX) to a terminating device, such as a telephone, when an off-hook condition is detected. It indicates that the exchange is working and is ready to initiate a telephone call. The tone stops when the first dialed digit is recognized. If no digits are forthcoming, the partial dial procedure is invoked, often eliciting a special information tone and an intercept message, followed by the off-hook tone, requiring the caller to hang up and redial.
Caller identification is a telephone service, available in analog and digital telephone systems, including voice over IP (VoIP), that transmits a caller's telephone number to the called party's telephone equipment when the call is being set up. The caller ID service may include the transmission of a name associated with the calling telephone number, in a service called Calling Name Presentation (CNAM). The service was first defined in 1993 in International Telecommunication Union—Telecommunication Standardization Sector (ITU-T) Recommendation Q.731.3.
The Automatic Voice Network was a worldwide American military telephone system. The system was built starting in 1963, based on the Army's existing Switch Communications Automated Network (SCAN) system.
A blue box is an electronic device, designed specifically for telephone toll fraud, that generates 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, either between a telephone operator switchboard or technician console and a switching machine, or machine to machine. First developed during the 1960s or possibly earlier, blue boxes allowed private individuals to call one number normally and redirect the call to a second number, with billing registering only the first number. The first number might be a toll free "800" or "information" number, a billable number, an unassigned number, or even, in some metropolitan areas, a local call. The call could be redirected to telephones elsewhere in North America or on many other continents, or, possibly, to ships at sea. Furthermore, the blue box gave the user access to numbers that were supposed to only be accessible to telephone operators and technicians.
An answering machine, answerphone or message machine, also known as telephone messaging machine in the UK and some Commonwealth countries, ansaphone or ansafone, or telephone answering device (TAD), is used for answering telephones and recording callers' messages. If a phone rings a number of times predetermined by the phone's owner, and nobody is present to answer the incoming call, the answering machine will activate and play either a generic announcement or the voice of the person being called announcing that nobody is able to come to the phone at the moment. Following the announcement is a beeping tone which prompts the caller to record a message after the tone concludes.
A busy signal in telephony is an audible call-progress tone or audible signal to the calling party that indicates failure to complete the requested connection of that particular telephone call.
A telephone call is a connection over a telephone network between the called party and the calling party.
Call waiting is a telecommunication service offered by a telephone service provider to a subscriber by which the subscriber may suspend a telephone call already in progress to accept a second call. The subscriber may switch between calls, typically by using the hook flash signal.
In telephony, call progress tones are audible tones that provide an indication of the status of a telephone call to the user. The tones are generated by a central office or a private branch exchange (PBX) to the calling party.
An intercept message is a telephone recording informing the caller that the call cannot be completed, for any of a number of reasons ranging from local congestion, to disconnection of the destination phone, number dial errors or network trouble along the route.
The precise tone plan is a signaling specification for the public switched telephone network (PSTN) in North America. It defines the call-progress tones used for indicating the status and progress of telephone calls to subscribers and operators.
The reorder tone, also known as the fast busy tone, or the congestion tone, or all trunks busy (ATB) tone is an audible call progress tone in the public switched telephone network (PSTN) that is returned to a calling party to indicate that the call cannot be processed through the network.
Ringing tone is a signaling tone in telecommunication that is heard by the originator of a telephone call while the destination terminal is alerting the receiving party. Audible ringing is typically a repeated tone that is not necessarily synchronous with the cadence of the power ringing signal that is sent to the called party.
A telephone number is a sequence of digits assigned to a fixed-line telephone subscriber station connected to a telephone line or to a wireless electronic telephony device, such as a radio telephone or a mobile telephone, or to other devices for data transmission via the public switched telephone network (PSTN) or other public and private networks.
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.
A telephone exchange, telephone switch, or central office is a telecommunications system used in the public switched telephone network (PSTN) or in large enterprises. It interconnects telephone subscriber lines or virtual circuits of digital systems to establish telephone calls between subscribers.
The Panel Machine Switching System is a type of automatic telephone exchange for urban service that was used in the Bell System in the United States for seven decades. The first semi-mechanical types of this design were installed in 1915 in Newark, New Jersey, and the last were retired in the same city in 1983.
