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.
An automated call distribution system, commonly known as automatic call distributor or automatic call dispatcher (ACD), is a telephony device that answers and distributes incoming calls to a specific group of terminals or agents within an organization. ACDs direct calls based on parameters that may include the caller's telephone number, the number they dialed, the time of day or a response to an automated voice prompt. Advanced ACD systems may use digital technologies such as computer telephony integration (CTI), computer-supported telecommunications applications (CSTA) or IVR as input to determine the route to a person or voice announcement that will serve the caller. Experts claim that "the invention of ACD technology made the concept of a call centre possible."
Pulse dialing is a signaling technology in telecommunications in which a direct current local loop circuit is interrupted according to a defined coding system for each signal transmitted, usually a digit. This lends the method the often used name loop disconnect dialing. In the most common variant of pulse dialing, decadic dialing, each of the ten Arabic numerals are encoded in a sequence of up to ten pulses. The most common version decodes the digits 1 through 9, as one to nine pulses, respectively, and the digit 0 as ten pulses. Historically, the most common device to produce such pulse trains is the rotary dial of the telephone, lending the technology another name, rotary dialing.
In telecommunication, signaling is the use of signals for controlling communications. This may constitute an information exchange concerning the establishment and control of a telecommunication circuit and the management of the network.
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 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. This allowed 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 as an incomplete call. A number of similar "color boxes" were also created to control other aspects of the phone network.
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 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.
Call waiting is a telephone service where a subscriber can accept a second incoming telephone call by placing an in-progress call on hold—and may also switch between calls. With some providers it can be combined with additional features such as conferencing, call forwarding, and caller ID. Call waiting is intended to alleviate the need to have more than one telephone line or number for voice communications.
The director telephone system was a development of the Strowger or step-by-step (SXS) switching system used in London and five other large cities in the UK from the 1920s to the 1980s.
A business telephone system is a telephone system typically used in business environments, encompassing the range of technology from the key telephone system (KTS) to the private branch exchange (PBX).
On analog telephone lines with special services, a flash or register-recall signal is used to control functions on the public telephone exchange, PBX or VoIP ATA.
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.
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.
Loop start is a telecommunications supervisory protocol between a central office or private branch exchange (PBX) and a subscriber telephone or other terminal for the purpose of starting and terminating a telephone call. It is the simplest of the telephone signaling systems, and uses the presence or absence of loop current to indicate the off-hook and on-hook loop states, respectively. It is used primarily for subscriber line signaling. An extension of the protocol that adds disconnect supervision is often called kewlstart.
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. The tone is typically a repeated cadence similar to a traditional power ringing signal (ringtone), but is usually not played synchronously. Various telecommunication groups, such as the Bell System and the General Post Office (GPO) developed standards, in part taken over by the European Telecommunications Standards Institute (ETSI) and other standards bodies. With modern cell phone and smartphone technology ringing tone can be customized and even used for advertising.
The push-button telephone is a telephone that has buttons or keys for dialing a telephone number, in contrast to having a rotary dial as in earlier telephone instruments.
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.
Dialling is the action of initiating a telephone call by operating the rotary dial or the telephone keypad of a telephone.
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.
