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Dialling (dialing in US English) is the action of initiating a telephone call by operating the rotary dial or the telephone keypad of a telephone.
| This section may contain material not related to the topic of the article .(October 2023) |
Dialling (dialing in US English) is the action of initiating a telephone call by operating the rotary dial or the telephone keypad of a telephone.
Prior to Strowgers invention of the step-by-step switch in 1891, telephone connections involved cranking a handle to generate a voltage that operated a bell on the remote operator's board; the operator would then get on the line to the subscriber and speak to them, they would then raise a voltage on the recipient's phone, alerting them of an incoming call. When this was acknowledged, the operator would patch the two subscribers together using a lead terminating in a jack plug. [1] [2]
Under Strowger's system, which was first introduced commercially in La Porte, Indiana, the number was dialled using two telegraph keys. The subscriber tapped eight times on one, then three times on the second to 'dial' the number 83. When this was introduced in Albion, New York in 1899, the keys were replaced by a rotary dial. [2]
From 1912, the British General Post Office, which also operated the British telephone system, installed several automatic telephone exchanges from several vendors in trials at Darlington on 10 October 1914 (rotary system), Fleetwood (relay exchange from Sweden), Grimsby (Siemens), Hereford (Lorimer) and Leeds (Strowger). [3] The BPO selected the Strowger switches for small and medium cities and towns. However, the selection of switching systems for London and other large cities was not decided until the 1920s, when the Director telephone system was adopted. The Director systems used SXS switches for destination routing and number translation facilities similar to the register used in common-control exchanges. Using similar equipment as in the rest of the network was deemed beneficial and the equipment could be manufactured in Britain.
Introduced to the public in 1963 by AT&T, Touch-Tone dialing greatly shortened the time of initiating a telephone call. It also enabled direct signaling from a telephone across the long-distance network using audio-frequency tones, which was impossible with the rotary dials that generated digital direct current pulses that had to be decoded by the local central office.
The touch tone key pad has sixteen keys laid out in a four-by-four matrix. Each key produces a combination of two audible tone frequencies, determined by their position on the pad. Each column and row has a distinct frequency assigned, thus generating a total of sixteen dual-tone multi-frequency (DTMF) signals. Early keypads only used the keys with the digits 1 through 9 and 0. The extra keys were intended for computer data entry, business functions, and military applications. By 1967, the keys with the asterisk (*) and hash (#) were added on all subscriber telephone sets. The keys A, B, C, D were used as priority signals (FO, F, I, and P) in the Automatic Voice Network (AUTOVON) of the US military.
Initial pushbutton designs employed mechanical switches, so that each button activated certain combinations of capacitors and inductors of an oscillator, while later versions used semiconductor logic chips to synthesize the frequencies. The tones are decoded by the receiver to determine the keys pressed by the user.
| 1209 Hz | 1336 Hz | 1477 Hz | 1633 Hz | |
|---|---|---|---|---|
| 697 Hz | ⓘ | ⓘ | ⓘ | ⓘ |
| 770 Hz | ⓘ | ⓘ | ⓘ | ⓘ |
| 852 Hz | ⓘ | ⓘ | ⓘ | ⓘ |
| 941 Hz | ⓘ | ⓘ | ⓘ | ⓘ |
For example, the key 1 produces a superimposition of tones of 697 and 1209 hertz (Hz).
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.
A rotary dial is a component of a telephone or a telephone switchboard that implements a signaling technology in telecommunications known as pulse dialing. It is used when initiating a telephone call to transmit the destination telephone number to a telephone exchange.
A telephone switchboard is a device used to connect circuits of telephones to establish telephone calls between users or other switchboards. The switchboard is an essential component of a manual telephone exchange, and is operated by switchboard operators who use electrical cords or switches to establish the connections.
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 telephony, ringdown is a method of signaling an operator in which telephone ringing current is sent over the line to operate a lamp or cause the operation of a self-locking relay known as a drop.
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 that employs analog signal transmission over copper loops. The term POTS originally stood for Post Office Telephone Service, as early telephone lines in many regions were operated directly by local Post Offices. For instance, in New Zealand, the telephone system remained under Post Office control until the 1980s.
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.
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.
The Strowger switch is the first commercially successful electromechanical stepping switch telephone exchange system. It was developed by the Strowger Automatic Telephone Exchange Company founded in 1891 by Almon Brown Strowger. Because of its operational characteristics, it is also known as a step-by-step (SXS) switch.
A telephone keypad is a keypad installed on a push-button telephone or similar telecommunication device for dialing a telephone number. It was standardized when the dual-tone multi-frequency signaling (DTMF) system was developed in the Bell System in the United States in the 1960s – this replaced rotary dialing, that had been developed for electromechanical telephone switching systems. Because of the abundance of rotary dial equipment still on use well into the 1990s, many telephone keypads were also designed to be backwards-compatible: as well as producing DTMF pulses, they could optionally be switched to produce loop-disconnect pulses electronically.
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, initially relying on analog systems. As technology advanced, the majority of telephone calls moved from traditional landlines to cellular networks and mobile phones. Telephone calls have also become common over the internet, using Voice over IP (VoIP) technology. They 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.
Automatic Electric Company was an American telephone equipment supplier primarily for independent telephone companies in North America, but also had a worldwide presence. With its line of automatic telephone exchanges, it was also a long-term supplier of switching equipment to the Bell System, starting in 1919. The company was the largest manufacturing unit of the Automatic Electric Group. In 1955, the company was acquired by General Telephone and Electronics (GT&E). After numerous reorganization within GTE, the company's assets came under the umbrella of Lucent in the 1990s, and subsequently part of Nokia.
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.
Tip and ring are the two conductors or sides of a telephone line. Their names are derived from the telephone plugs used for connecting telephone calls in manual switchboards. One side of the line is connected to the metal tip of the plug, and the second is connected to a metal ring behind the tip, separated and insulated from the tip by a non-conducting material. When inserted into a jack, the plug's tip conductor connects first, followed by the ring conductor. In many European countries, tip and ring are referred to as the A and B wires.
A push-button telephone is a telephone that has buttons or keys for dialing a telephone number, in contrast to a rotary dial used in earlier telephones.
A telephone exchange, also known as a telephone switch or central office, is a crucial component in the public switched telephone network (PSTN) or large enterprise telecommunications systems. It facilitates the interconnection of telephone subscriber lines or digital system virtual circuits, enabling telephone calls between subscribers.
A group switching centre (GSC) was a United Kingdom telephone exchange used to provide local and trunk routing to local exchanges within its own and if required, adjacent group areas.
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.