Misplaced Pages

#893106

55-560: 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

110-470: A calendar issued by the TSB. SGs are augmented by Focus Groups (FGs), an instrument created by ITU-T, providing a way to quickly react to ICT standardization needs and allowing great flexibility in terms of participation and working methods. The key difference between SGs and FGs is that the latter have greater freedom to organize and finance themselves, and to involve non-members in their work, but they do not have

165-507: A function that is performed in the United States by Bell 202 modulated frequency-shift keying (FSK) signaling. DTMF was originally decoded by tuned filter banks . By the end of the 20th century, digital signal processing became the predominant technology for decoding. DTMF decoding algorithms typically use the Goertzel algorithm although application of MUSIC (algorithm) to DTMF decoding has been shown to outperform Goertzel and being

220-507: A key sends a combination of the row and column frequencies. For example, the 1 key produces a superimposition of a 697 Hz low tone and a 1209 Hz high tone. Initial pushbutton designs employed levers, enabling each button to activate one row and one column contact. The tones are decoded by the switching center to determine the keys pressed by the user. Engineers had envisioned telephones being used to access computers and automated response systems. They consulted with companies to determine

275-449: A loop-disconnect (LD) signaling, more commonly known as pulse dialing (dial pulse, DP) in the United States. It functions by interrupting the current in the local loop between the telephone exchange and the calling party 's telephone at a precise rate with a switch in the telephone that is operated by the rotary dial as it spins back to its rest position after having been rotated to each desired number. The exchange equipment responds to

330-674: A number is a priority call. Present-day uses of the signals A, B, C and D are rare in telephone networks, and are exclusive to network control. For example, A is used in some networks for cycling through a list of carriers. The signals are used in radio phone patch and repeater operations to allow, among other uses, control of the repeater while connected to an active telephone line. The signals *, #, A, B, C and D are still widely used worldwide by amateur radio operators and commercial two-way radio systems for equipment control, repeater control, remote-base operations and some telephone communications systems. DTMF signaling tones may also be heard at

385-469: A part of signaling protocols, as long as both endpoints agree on a common approach to adopt. The DTMF telephone keypad is laid out as a matrix of push buttons in which each row represents the low frequency component and each column represents the high frequency component of the DTMF signal. The commonly used keypad has four rows and three columns, but a fourth column is present for some applications. Pressing

440-416: A profusion of software firms around the world were still furiously competing to shape the future of the electronic office , and was completed in 1999 long after Microsoft Office 's then-secret binary file formats had become established as the global de facto standard. The ITU-T now operates under much more streamlined processes. The time between an initial proposal of a draft document by a member company and

495-807: A similar form. At the initiative of Napoleon III , the French government invited international participants to a conference in Paris in 1865 to facilitate and regulate international telegraph services. A result of the conference was the founding of the forerunner of the modern ITU. At the 1925 Paris conference, the ITU created two consultative committees to deal with the complexities of the international telephone services, known as CCIF ( Comité Consultatif International Téléphonique ) and with long-distance telegraphy CCIT ( Comité Consultatif International des Communications Téléphoniques à grande distance ). In view of

550-473: A wide array of topics in the field of information and communication technologies (ICT) and attract high-ranking experts as speakers, and attendees from engineers to high-level management from all industry sectors. The technical work, the development of Recommendations, of ITU-T is managed by Study Groups (SGs), such as Study Group 13 for network standards, Study Group 16 for multimedia standards, and Study Group 17 for security standards, which are created by

605-582: Is a fast-track approval procedure that was developed to allow standards to be brought to market in the timeframe that industry now demands. The AAP is defined in ITU-T Recommendation A.8. This dramatic overhaul of standards-making by streamlining approval procedures was implemented in 2001 and is estimated to have cut the time involved in this critical aspect of the standardization process by 80 to 90 percent. This means that an average standard that took around four years to approve and publish until

SECTION 10

#1732773285894

660-407: Is a group of signaling methods that use a mixture of two pure tone (pure sine wave ) sounds. Various MF signaling protocols were devised by the Bell System and CCITT . The earliest of these were for in-band signaling between switching centers, where long-distance telephone operators used a 16- digit keypad to input the next portion of the destination telephone number in order to contact

715-506: Is able to convey multiple items of formation (e.g. multiple digits of the called telephone number). Subscriber signaling refers to the signaling between the telephone and the telephone exchange . Trunk signaling is the signaling between exchanges. Every signaling system can be characterized along each of the above axes of classification. A few examples: Whereas common-channel signaling systems are out-of-band by definition, and in-band signaling systems are also necessarily channel-associated,

770-407: Is concerned with conveying addressing information, such as the calling and/or called telephone number . In the early days of telephony , with operator handling calls, the addressing formation is by voice as "Operator, connect me to Mr. Smith please". In the first half of the 20th century, addressing formation is done by using a rotary dial , which rapidly breaks the line current into pulses , with

825-616: Is followed by a period and the Recommendation number, which uniquely identifies the Recommendation within the series. Often, a range of related Recommendations are further grouped within the series and given adjacent numbers, such as "H.200-H.499: Infrastructure of audiovisual services" or "H.260-H.279: Coding of moving video". Many numbers are "skipped" to give room for future Recommendations to be adjacent to related Recommendations. Recommendations can be revised or "superseded" and keep their existing Recommendation number. In addition to

880-460: Is now free of charge online. (About 30 specifications jointly maintained by the ITU-T and ISO/IEC are not available for free to the public. ) ITU-T has moreover tried to facilitate cooperation between the various forums and standard-developing organizations (SDOs). This collaboration is necessary to avoid duplication of work and the consequent risk of conflicting standards in the market place. In

935-503: Is standardized as ITU-T Recommendation Q.23. It is also known in the UK as MF4 . Touch-tone dialing with a telephone keypad gradually replaced the use of rotary dials and has become the industry standard in telephony to control automated equipment and signal user intent. Other multi-frequency systems are also used for signaling on trunks in the telephone network. Before the development of DTMF, telephone numbers were dialed by users with

990-416: 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. Signaling systems may be classified based on several principal characteristics. In the public switched telephone network (PSTN), in-band signaling is the exchange of call control information within

1045-851: The Plenipotentiary Conference (the top policy-making conference of ITU) saw a reform of ITU, giving the Union greater flexibility to adapt to an increasingly complex, interactive and competitive environment. The CCITT was renamed the Telecommunication Standardization Sector (ITU-T), as one of three Sectors of the Union alongside the Radiocommunication Sector ( ITU-R ) and the Telecommunication Development Sector ( ITU-D ). Historically,

1100-642: The World Telecommunication Standardization Assembly (WTSA) which is held every four years. As part of the deliberations, WTSA has instructed ITU to hold the Global Standards Symposium , which unlike WTSA is open to public for participation. The people involved in these SGs are experts in telecommunications from all over the world. There are currently 11 SGs. Study groups meet face to face (or virtually under exceptional circumstances) according to

1155-639: The DTMF specification, that indicate the status of lines, equipment, or the result of calls, and for control of equipment for troubleshooting or service purposes. Such call-progress tones are often also composed of multiple frequencies and are standardized in each country. The Bell System defined them in the Precise Tone Plan . Bell's Multi-frequency signaling was exploited by blue box devices. Some early modems were based on touch-tone frequencies, such as Bell 400-style modems. Telecommunication signaling In telecommunications , signaling

SECTION 20

#1732773285894

1210-868: The ITU-T Recommendations, which have non-mandatory status unless they are adopted in national laws, ITU-T is also the custodian of a binding international treaty, the International Telecommunication Regulations. The ITRs go back to the earliest days of the ITU when there were two separate treaties, dealing with telegraph and telephone. The ITRs were adopted, as a single treaty, at the World Administrative Telegraphy and Telephone Conference held in Melbourne, 1988 (WATTC-88). The ITRs comprise ten articles which deal, inter alia , with

1265-473: The ITU-T are referred to as " Recommendations " (with the word capitalized to distinguish its meaning from the common parlance sense of the word "recommendation"), as they become mandatory only when adopted as part of a national law. Since the ITU-T is part of the ITU, which is a United Nations specialized agency, its standards carry more formal international weight than those of most other standards development organizations that publish technical specifications of

1320-523: The Recommendations of the CCITT were presented at plenary assemblies for endorsement, held every four years, and the full set of Recommendations were published after each plenary assembly. However, the delays in producing texts, and translating them into other working languages, did not suit the fast pace of change in the telecommunications industry. The rise of the personal computer industry in

1375-476: The SG chairman, in consultation with TSB, sets up a comment resolution process by the concerned experts. The revised text is then posted on the web for an additional review period of three weeks. Similar to the last call phase, in additional review the Recommendation is considered as approved if no comments are received. If comments are received, it is apparent that there are some issues that still need more work, and

1430-540: The TSB is Seizo Onoe (of Japan), whose 4-year term commenced on 1 January 2023. Seizo Onoe succeeded Chaesub Lee of South Korea, who was director from 1 January 2015 until 31 December 2022. The ITU-T mission is to ensure the efficient and timely production of standards covering all fields of telecommunications and Information Communication Technology (ICTs) on a worldwide basis, as well as defining tariff and accounting principles for international telecommunication services. The international standards that are produced by

1485-628: The Touch-Tone feature tone dialing or DTMF . Automatic Electric (GTE) referred to it as "Touch-calling" in their marketing. Other trade names such as Digitone were used by the Northern Electric Company in Canada. As a method of in-band signaling , DTMF signals were also used by cable television broadcasters as cue tones to indicate the start and stop times of local commercial insertion points during station breaks for

1540-557: The United States and Canada to suppress caller ID . Public payphones that accept credit cards use these additional codes to send the information from the magnetic strip . The AUTOVON telephone system of the United States Armed Forces used signals A, B, C, and D to assert certain privilege and priority levels when placing telephone calls. Precedence is still a feature of military telephone networks, but using number combinations. For example, entering 93 before

1595-601: The above metering pulse example demonstrates that there exist channel-associated signaling systems which are out-of-band. ITU-T The World Telecommunication Standardization Assembly (WTSA), the sector's governing conference, convenes every four years. ITU-T has a permanent secretariat called the Telecommunication Standardization Bureau (TSB), which is based at the ITU headquarters in Geneva, Switzerland . The current director of

1650-459: The advent of digital trunks , supervision signals are carried by robbed bits or other bits in the E1-carrier dedicated to signaling. Line signaling is concerned with conveying information on the state of the line or channel, such as on-hook, off-hook (answer supervision and disconnect supervision, together referred to as supervision ), ringing , and hook flash . Register signaling

1705-579: The amendment of ITRs through a World Conference on International Telecommunications (WCIT). Accordingly, in 1998 there began a process of review of the ITRs; and in 2009 extensive preparations began for such a conference, WCIT-12. In addition to "regional preparatory meetings", the ITU Secretariat developed 13 "Background Briefs on key issues" that were expected to be discussed at the conference. Convened by former ITU secretary-general Hamadoun Touré,

DTMF - Misplaced Pages Continue

1760-429: The approval process by providing equal opportunities for both sector members and member states in the approval of technical standards. A panel of SG experts drafts a proposal that is then forwarded at an SG meeting to the appropriate body which decides if it is sufficiently ready to be designated a draft text and thus gives its consent for further review at the next level. After this Consent has been given, TSB announces

1815-595: The authority to approve Recommendations. Focus Groups can be created very quickly, are usually short-lived and can choose their own working methods, leadership, financing, and types of deliverables. Current Focus Groups include the ITU-WHO Focus Group on Artificial Intelligence for Health (FG-AI4H) as well as Machine Learning for 5G (which developed Y.3172 ), Quantum Information Technologies for Networks , and Artificial Intelligence for Assisted and Autonomous Driving . The Alternative Approval Process (AAP)

1870-711: The basic similarity of many of the technical problems faced by the CCIF and CCIT , a decision was taken in 1956 to merge them into a single entity, the International Telegraph and Telephone Consultative Committee ( CCITT , in French : Comité Consultatif International Téléphonique et Télégraphique ). The first Plenary Assembly of the new organization was held in Geneva, Switzerland in December 1956. In 1992,

1925-436: The benefit of cable companies. Until out-of-band signaling equipment was developed in the 1990s, fast, unacknowledged DTMF tone sequences could be heard during the commercial breaks of cable channels in the United States and elsewhere. Previously, terrestrial television stations used DTMF tones to control remote transmitters. In IP telephony , DTMF signals can also be delivered as either in-band or out-of-band tones, or even as

1980-522: The definition of international telecommunication services, cooperation between countries and national administrations, safety of life and priority of telecommunications and charging and accounting principles. The adoption of the ITRs in 1988 is often taken as the start of the wider liberalization process in international telecommunications, though a few countries, including United States and United Kingdom, had made steps to liberalize their markets before 1988. The Constitution and Convention of ITU provides for

2035-546: The dial pulses either directly by operating relays or by storing the number in a digit register that records the dialed number. The physical distance for which this type of dialing was possible was restricted by electrical distortions and was possible only on direct metallic links between end points of a line. Placing calls over longer distances required either operator assistance or provision of special subscriber trunk dialing equipment. Operators used an earlier type of multi-frequency signaling. Multi-frequency signaling ( MF )

2090-601: The draft text and all comments are sent to the next Study Group meeting for further discussion and possible approval. Those Recommendations considered as having policy or regulatory implications are approved through what is known as the Traditional Approval Process (TAP), which allows a longer period for reflection and commenting by member states. TAP Recommendations are also translated into the six working languages of ITU (Arabic, Chinese, English, French, Russian, and Spanish). ITU-T Recommendations are

2145-505: The early 1980s created a new common practice among both consumers and businesses of adopting " bleeding edge " communications technology even if it was not yet standardized. Thus, standards organizations had to put forth standards much faster, or find themselves ratifying de facto standards after the fact. One of the most prominent examples of this was the Open Document Architecture project, which began in 1985 when

2200-412: The final approval of a full-status ITU-T Recommendation can now be as short as a few months (or less in some cases). This makes the standardization approval process in the ITU-T much more responsive to the needs of rapid technology development than in the ITU's historical past. New and updated Recommendations are published on an almost daily basis, and nearly all of the library of over 3,270 Recommendations

2255-518: The mid nineties, and two years until 1997, can now be approved in an average of two months, or as little as five weeks. Besides streamlining the underlying procedures involved in the approval process, an important contributory factor to the use of AAP is electronic document handling. Once the approval process has begun the rest of the process can be completed electronically, in the vast majority of cases, with no further physical meetings. The introduction of AAP also formalizes public/private partnership in

DTMF - Misplaced Pages Continue

2310-421: The names given to telecommunications and computer protocol specification documents published by ITU-T. ITU-T assigns each Recommendation a name based on the series and Recommendation number. The name starts with the letter of the series the Recommendation belongs to. Each series encompasses a broad category of Recommendations, such as "H-Series Recommendations: Audiovisual and multimedia systems". The series letter

2365-481: The next downstream long-distance telephone operator. This semi-automated signaling and switching proved successful in both speed and cost effectiveness. Based on this prior success with using MF by specialists to establish long-distance telephone calls, dual-tone multi-frequency signaling was developed for end-user signaling without the assistance of operators. The DTMF system uses a set of eight audio frequencies transmitted in pairs to represent 16 signals, represented by

2420-506: The number of pulses conveying the address. Finally, starting in the second half of the century, address signaling is by DTMF . Channel-associated signaling (CAS) employs a signaling channel that is dedicated to a specific bearer channel . Common-channel signaling (CCS) employs a signaling channel which conveys signaling information relating to multiple bearer channels. These bearer channels, therefore, have their signaling channel in common. Compelled signaling refers to signaling where

2475-456: The only possibility in cases when number of available samples is limited. As DTMF signaling is often transmitted in-band with voice or other audio signals present simultaneously, the DTMF signal definition includes strict limits for timing (minimum duration and interdigit spacing), frequency deviations, harmonics, and amplitude relation of the two components with respect to each other ( twist ). National telephone systems define other tones, outside

2530-473: The receipt of each signal from an originating register needs to be explicitly acknowledged before the next signal can be sent. Most forms of R2 register signaling are compelled, while R1 multi-frequency signaling is not. The term is only relevant in the case of signaling systems that use discrete signals (e.g. a combination of tones to denote one digit), as opposed to signaling systems which are message-oriented (such as SS7 and ISDN Q.931) where each message

2585-461: The requirements. This led to the addition of the number sign (#, ''pound'' or "diamond" in this context, "hash", "square" or "gate" in the UK, and " octothorpe '' by the original engineers) and asterisk or "star" (*) keys as well as a group of keys for menu selection: A, B, C and D. In the end, the lettered keys were dropped from most keypads and it was many years before the two symbol keys became widely used for vertical service codes such as *67 in

2640-425: The same physical channel, or within the same frequency band, that the message (the callers' voice) is using. An example is dual-tone multi-frequency signaling (DTMF), which is used on most telephone lines to customer premises. Out-of-band signaling is telecommunication signaling on a dedicated channel separate from that used for the message. Out-of-band signaling has been used since Signaling System No. 6 (SS6)

2695-414: The start and/or end of some prerecorded VHS videocassettes. Information on the master version of the video tape is encoded in the DTMF tones. The encoded tones provide information to automatic duplication machines, such as format, duration and volume levels in order to replicate the original video as closely as possible. DTMF tones are used in some caller ID systems to transfer the caller ID information,

2750-549: The start of the AAP procedure by posting the draft text to the ITU-T website and calling for comments. This gives the opportunity for all members to review the text. This phase, called last call , is a four-week period in which comments can be submitted by member states and sector members. If no comments other than editorial corrections are received, the Recommendation is considered approved since no issues were identified that might need any further work. However, if there are any comments,

2805-412: The ten digits, the letters A to D, and the symbols # and * . As the signals are audible tones in the voice frequency range, they can be transmitted through electrical repeaters and amplifiers, and over radio and microwave links, thus eliminating the need for intermediate operators on long-distance circuits. AT&T described the product as "a method for pushbutton signaling from customer stations using

SECTION 50

#1732773285894

2860-472: The trademark Touch-Tone . The term was first used by AT&T in commerce on July 5, 1960, and was introduced to the public on November 18, 1963, when the first push-button telephone was made available to the public. As a parent company of Bell Systems, AT&T held the trademark from September 4, 1962, to March 13, 1984. It is standardized by ITU-T Recommendation Q.23. In the UK, it is also known as MF4. Other vendors of compatible telephone equipment called

2915-516: The voice transmission path". In order to prevent consumer telephones from interfering with the MF-based routing and switching between telephone switching centers, DTMF frequencies differ from all of the pre-existing MF signaling protocols between switching centers: MF/R1, R2 , CCS4, CCS5, and others that were later replaced by SS7 digital signaling. DTMF was known throughout the Bell System by

2970-637: The work of standardization, ITU-T cooperates with other SDOs, e.g., the International Organization for Standardization (ISO) and the Internet Engineering Task Force (IETF). Most of the work of ITU-T is carried out by its Sector Members and Associates, while the Telecommunication Standardization Bureau (TSB) is the executive arm of ITU-T and coordinator for a number of workshops and seminars to progress existing work areas and explore new ones. The events cover

3025-564: Was introduced in the 1970s, and also in Signalling System No. 7 (SS7) in 1980 which became the standard for signaling among exchanges internationally. In the mid-20th century, supervision signals on long-distance trunks in North America were primarily in-band, for example at 2600 Hz , necessitating a notch filter to prevent interference. Late in the century, all supervisory signals had been moved out of band. With

#893106