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Dual-tone Multi-frequency Signalling
Dual-tone multi-frequency signaling (DTMF) is a Signalling (telecommunications), telecommunication signaling system using the voice-frequency band over telephone lines between telephone equipment and other communications devices and Automatic telephone exchange, 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''. The Touch-Tone system using a telephone keypad gradually replaced the use of rotary dial and has become the industry standard for landline and mobile service. Other multi-frequency systems are used for internal signaling within the telephone network. Multifrequency signaling Before the development of DTMF, telephone numbers were dialed by users with a loop-disconnect (LD) signaling, more commonly known as pulse diali ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Communications Protocol
A communication protocol is a system of rules that allows two or more entities of a communications system to transmit information via any kind of variation of a physical quantity. The protocol defines the rules, syntax, semantics and synchronization of communication and possible error recovery methods. Protocols may be implemented by hardware, software, or a combination of both. Communicating systems use well-defined formats for exchanging various messages. Each message has an exact meaning intended to elicit a response from a range of possible responses pre-determined for that particular situation. The specified behavior is typically independent of how it is to be implemented. Communication protocols have to be agreed upon by the parties involved. To reach an agreement, a protocol may be developed into a technical standard. A programming language describes the same for computations, so there is a close analogy between protocols and programming languages: ''protocols ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Cue Tone
Cue or CUE may refer to: Event markers *Sensory cue, in perception (experimental psychology) *Cue (theatrical), the trigger for an action to be carried out at a specific time, in theatre or film *Cue (show control), the electronic rendering of the specific action(s) to be carried out at a specific time by a show control system *Voice cue, in dance, words or sounds that help match rhythmic patterns of steps with the music *Cue mark, in motion picture film to signal projectionists of reel changes *Cue, a vocal message given by a group fitness instructor to inform participants of upcoming sequences, such as a change in stretching direction Music and audio * Cue (band), a Swedish musical group * Cue tone, a message consisting of audio tones, used to prompt an action. * Cue (audio), to determine the desired initial playback point in a piece of recorded music *Cue sheet (computing), a metadata file that describes how the tracks of an audio track are laid out *Source cue, music that eman ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Broadcasting
Broadcasting is the distribution of audio or video content to a dispersed audience via any electronic mass communications medium, but typically one using the electromagnetic spectrum (radio waves), in a one-to-many model. Broadcasting began with AM radio, which came into popular use around 1920 with the spread of vacuum tube radio transmitters and receivers. Before this, all forms of electronic communication (early radio, telephone, and telegraph) were one-to-one, with the message intended for a single recipient. The term ''broadcasting'' evolved from its use as the agricultural method of sowing seeds in a field by casting them broadly about. It was later adopted for describing the widespread distribution of information by printed materials or by telegraph. Examples applying it to "one-to-many" radio transmissions of an individual station to multiple listeners appeared as early as 1898. Over the air broadcasting is usually associated with radio and television, though m ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Cable Television
Cable television is a system of delivering television programming to consumers via radio frequency (RF) signals transmitted through coaxial cables, or in more recent systems, light pulses through fibre-optic cables. This contrasts with broadcast television (also known as terrestrial television), in which the television signal is transmitted over-the-air by radio waves and received by a television antenna attached to the television; or satellite television, in which the television signal is transmitted over-the-air by radio waves from a communications satellite orbiting the Earth, and received by a satellite dish antenna on the roof. FM radio programming, high-speed Internet, telephone services, and similar non-television services may also be provided through these cables. Analog television was standard in the 20th century, but since the 2000s, cable systems have been upgraded to digital cable operation. A "cable channel" (sometimes known as a "cable network") is a ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
In-band Signaling
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. Telephony When dialing from a land-line telephone, the telephone number is encoded and transmitted across the telephone line in form of dual-tone multi-frequency signaling (DTMF). The tones control the telephone system by instructing the telephone switch where to route the call. These control tones are sent over the same channel, the copper wire, and in the frequency range (300 Hz to 3.4 kHz) as the audio of the ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Northern Electric Company
Nortel Networks Corporation (Nortel), formerly Northern Telecom Limited, was a Canadian multinational telecommunications and data networking equipment manufacturer headquartered in Ottawa, Ontario, Canada. It was founded in Montreal, Quebec, in 1895 as the Northern Electric and Manufacturing Company. Until an antitrust settlement in 1949, Northern Electric was owned principally by Bell Canada and the Western Electric Company of the Bell System, producing large volumes of telecommunication equipment based on licensed Western Electric designs. At its height, Nortel accounted for more than a third of the total valuation of all companies listed on the Toronto Stock Exchange (TSX), employing 94,500 people worldwide. In 2009, Nortel filed for bankruptcy protection in Canada and the United States, triggering a 79% decline of its corporate stock price. The bankruptcy case was the largest in Canadian history and left pensioners, shareholders and former employees with enormous losses. B ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Signalling System No 7
Signalling System No. 7 (SS7) is a set of telephony signaling protocols developed in 1975, which is used to set up and tear down telephone calls in most parts of the world-wide public switched telephone network (PSTN). The protocol also performs number translation, local number portability, prepaid billing, Short Message Service (SMS), and other services. The protocol was introduced in the Bell System in the United States by the name ''Common Channel Interoffice Signaling'' in the 1970s for signalling between No. 4ESS switch and No. 4A crossbar toll offices. In North America SS7 is also often referred to as ''Common Channel Signaling System 7'' (CCSS7). In the United Kingdom, it is called ''C7'' (CCITT number 7), ''number 7'' and ''Common Channel Interoffice Signaling 7'' (CCIS7). In Germany, it is often called ''Zentraler Zeichengabekanal Nummer 7'' (ZZK-7). The SS7 protocol is defined for international use by the Q.700-series recommendations of 1988 by the ITU-T. Of the many ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
R2 Signalling
Signalling System R2 is a signalling protocol for telecommunications that was in use from the 1960s mostly in Europe, and later also in Latin America, Asia, and Australia, to convey exchange information between two telephone switching systems for establishing a telephone call via a telephone trunk.ITU-T Recommendation Q.400-Q.490 - Specifications of Signalling System R2 It is suitable for signaling on analog as well as digital circuits. R2 signaling specifications were first published by the International Telegraph and Telephone Consultative Committee (CCITT) in ITU White Book Volume VI of 1969,IVth Plenary Assembly (Mar Del Plata, 23 September-25 October 1968), White Book Volume VI, ''Telephone Signaling and Switching'', Recommendations Series Q, ITU 1969. and are maintained by the [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Keypad
A keypad is a block or pad of buttons set with an arrangement of digits, symbols, or alphabetical letters. Pads mostly containing numbers and used with computers are numeric keypads. Keypads are found on devices which require mainly numeric input such as calculators, television remotes, push-button telephones, vending machines, ATMs, point of sale terminals, combination locks, safes, and digital door locks. Many devices follow the E.161 standard for their arrangement. Uses and functions A computer keyboard usually has a small numeric keypad on the side, in addition to the other number keys on the top, but with a calculator-style arrangement of buttons that allow more efficient entry of numerical data. This number pad (commonly abbreviated to ''numpad'') is usually positioned on the right side of the keyboard because most people are right-handed. Many laptop computers have special function keys that turn part of the alphabetical keyboard into a numerical keypad as there ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Numerical Digit
A numerical digit (often shortened to just digit) is a single symbol used alone (such as "2") or in combinations (such as "25"), to represent numbers in a positional numeral system. The name "digit" comes from the fact that the ten digits (Latin ''digiti'' meaning fingers) of the hands correspond to the ten symbols of the common base 10 numeral system, i.e. the decimal (ancient Latin adjective ''decem'' meaning ten) digits. For a given numeral system with an integer base, the number of different digits required is given by the absolute value of the base. For example, the decimal system (base 10) requires ten digits (0 through to 9), whereas the binary system (base 2) requires two digits (0 and 1). Overview In a basic digital system, a numeral is a sequence of digits, which may be of arbitrary length. Each position in the sequence has a place value, and each digit has a value. The value of the numeral is computed by multiplying each digit in the sequence by ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Switchboard Operator
In the early days of telephony, companies used manual telephone switchboards, and switchboard operators connected calls by inserting a pair of phone plugs into the appropriate jacks. They were gradually phased out and replaced by automated systems, first those allowing direct dialing within a local area, then for long-distance and international direct dialing. Description A typical telephone switchboard has a vertical panel containing an array of jacks with a desk in front. The desk has a row of switches and two rows of plugs attached to cables that retract into the desk when not in use. Each pair of plugs was part of a cord circuit with a switch associated that let the operator participate in the call or ring the circuit for an incoming call. Each jack had a light above it that lit when the customer's telephone receiver was lifted (the earliest systems required the customer to hand-crank a magneto to alert the central office and, later, to "ring off" the completed call). Lin ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
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