Signaling (telecommunications)

In the public switched telephone network (PSTN), in-band signaling is the exchange of call control information within the same physical channel, or within the same frequency band, that the telephone call itself 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 telephone call. Out-of-band signaling has been used since Signaling System No. 6 (SS6) was introduced in the 1970s, and also in Signalling System No. 7 (SS7) in 1980 which became the standard for signaling among exchanges ever since.

Subscriber identity module

SIMSIM cardnano-SIM
A subscriber identity module or subscriber identification module (SIM), widely known as a SIM card, is an integrated circuit that is intended to securely store the international mobile subscriber identity (IMSI) number and its related key, which are used to identify and authenticate subscribers on mobile telephony devices (such as mobile phones and computers). It is also possible to store contact information on many SIM cards. SIM cards are always used on GSM phones; for CDMA phones, they are only needed for newer LTE-capable handsets. SIM cards can also be used in satellite phones, smart watches, computers, or cameras.

Wideband audio

HD Voicewidebandwideband voice
Wideband audio, also known as wideband voice or HD voice, is high definition voice quality for telephony audio, contrasted with standard digital telephony "toll quality". It extends the frequency range of audio signals transmitted over telephone lines, resulting in higher quality speech. The range of the human voice extends from 80 Hz to 14 kHz but traditional, voiceband or narrowband telephone calls limit audio frequencies to the range of 300 Hz to 3.4 kHz. Wideband audio relaxes the bandwidth limitation and transmits in the audio frequency range of 50 Hz to 7 kHz or even up to 22 kHz.


Many mobile phones and portable devices such as Apple's iPod Nano, or Sony's PlayStation Portable use LDTV video, as higher-resolution files would be excessive to the needs of their small screens (320×240 and 480×272 pixels respectively). The current generation of iPod Nanos have LDTV screens, as do the first three generations of iPod Touch and iPhone (480×320). For the first years of its existence, YouTube offered only one, low-definition resolution of 320x240p at 30fps or less. A standard, consumer grade VHS videotape can be considered SDTV due to its resolution (approximately 360 × 480i/576i).

Automatic number identification

ANIthe caller's numberautomatic number identification (ANI)
Modern toll-free telephone numbers, which generate itemized billing of all calls received instead of relying on the special fixed-rate trunks of the Bell System's original Inward WATS service, depend on ANI to track inbound calls to numbers in special area codes such as +1-800, 888, 877, 866, 855, 844 with 833 and 822 reserved for future toll free use (United States and Canada), 1800 (Australia) or 0800 and 0808 (United Kingdom). ANI is different, conceptually and technically, from caller ID service. A caller's telephone number and line type are captured by ANI service even if caller ID blocking is activated.

Pulse-code modulation

It is the standard form of digital audio in computers, compact discs, digital telephony and other digital audio applications. In a PCM stream, the amplitude of the analog signal is sampled regularly at uniform intervals, and each sample is quantized to the nearest value within a range of digital steps. Linear pulse-code modulation (LPCM) is a specific type of PCM where the quantization levels are linearly uniform. This is in contrast to PCM encodings where quantization levels vary as a function of amplitude (as with the A-law algorithm or the μ-law algorithm). Though PCM is a more general term, it is often used to describe data encoded as LPCM.

Telephone exchange names

central office nametelephone exchangetelephone exchange name
This extended the usable numbering plan and only two area code splits became necessary between 1962 and 1981. All-number calling was phased in starting in 1958 and most areas had adopted it fully by the mid-1960s. In some areas it did not become universal until the 1980s. The Bell System published and distributed area code handbooks yearly which compiled the towns available for calling using an area code. Experiencing significant resistance in many areas, the Bell System employed a strategy of gradual changes to ease the transition for customers.

Access network

accessaccess attemptaccess networks
Access is essential to the future profitability of operators who are experiencing massive reductions in revenue from plain old telephone services, due in part to the opening of historically nationalized companies to competition, and in part to increased use of mobile phones and voice over IP (VoIP) services. Operators offered additional services such as xDSL based broadband and IPTV (Internet Protocol Television) to guarantee profit. The access network is again the main barrier to achieving these profits since operators worldwide have accurate records of only 40% to 60% of the network.

Premium-rate telephone number

premium rate900 number1-900
Premium-rate telephone numbers are telephone numbers for telephone calls during which certain services are provided, and for which prices higher than normal are charged. Unlike a normal call, part of the call charge is paid to the service provider, thus enabling businesses to be funded via the calls. While the billing is different, calls are usually routed the same way they are for a toll-free telephone number, being anywhere despite the area code used. These telephone numbers are usually allocated from a national telephone numbering plan in such a way that they are easily distinguished from other numbers.


CCITTTelecommunication Standardization SectorComité Consultatif International Téléphonique et Télégraphique
Data communication over the telephone network, V-series. Fax standards T.2 – T.4, T.30, T.37, T.38. (Next generation wired home networking over powerlines, phonelines and coaxial cable). Green ICT standards and supplements ( L.1000 series). H.323 family of standards for multimedia and VoIP. Interconnection rate harmonization, D-series. International Emergency Preference Scheme E.106. IMSI codes used in SIM cards E.212. ISDN and PSTN/3G videoconferencing systems, H.320 and H.324. ISDN (Integrated Services Digital Network) Q.931. Open Systems Interconnection. Optical Transport Network (OTN) G.709, G.798, G.872. Passive optical networks (PON) G.983, G.984, G.987.

Disruptive innovation

disruptive technologydisruptive technologiesdisruptive
In business, a disruptive innovation is an innovation that creates a new market and value network and eventually disrupts an existing market and value network, displacing established market-leading firms, products, and alliances. The term was defined and first analyzed by the American scholar Clayton M. Christensen and his collaborators beginning in 1995, and has been called the most influential business idea of the early 21st century.

Bruce Almighty

Since God contacts Bruce using an actual phone number rather than a number in the standard fictional 555 telephone exchange, several people and groups sharing this number subsequently received hundreds of phone calls from people wanting to talk to God, including a church in North Carolina (where the Minister was named Bruce), a Pastor in Northern Wisconsin and a man in Manchester, England. The producers noted that the number (776-2323) was not in use in the area code (716, which was never specified on screen) in the film's story but did not check anywhere else. The home video and television versions changed it to the fictional 555-0123.

Call centre

call centercall centerscall centres
In virtual call centre model, the call centre operator pays a monthly or annual fee to a vendor that hosts the call centre telephony equipment in their own data centre. In this model, the operator does not own, operate or host the equipment that the call centre runs on. Agents connect to the vendor's equipment through traditional PSTN telephone lines, or over voice over IP. Calls to and from prospects or contacts originate from or terminate at the vendor's data centre, rather than at the call centre operator's premises. The vendor's telephony equipment then connects the calls to the call centre operator's agents.

Called party

calleecall receivercalled
The called party also pays if the number dialed is a toll-free telephone number. In some countries such as Canada, the United States and China, users of mobile phones pay for the "airtime" to receive calls. In most other countries (e.g. most European countries), the elevated interconnect fees are paid fully by the calling party and the called party incurs no charge. de:B-Teilnehmer


wifiwireless internetwireless
The United Kingdom's Health Protection Agency reported in 2007 that exposure to Wi-Fi for a year results in the "same amount of radiation from a 20-minute mobile phone call". A review of studies involving 725 people who claimed electromagnetic hypersensitivity, "...suggests that 'electromagnetic hypersensitivity' is unrelated to the presence of an EMF, although more research into this phenomenon is required."

Direct inward dial

direct inward dialingdirect inbound dialingDID
To allow public switched telephone network (PSTN) users to directly reach users with VoIP phones, DID numbers are assigned to a communications gateway. The gateway connects the PSTN to the VoIP network, routing and translating calls between the two networks. In countries with multiple competing local providers, DID services can be purchased in bulk from a Competitive Local Exchange Carrier (CLEC). For voice over IP resellers, some specialized CLECs (for local numbers) or interexchange carriers (for toll-free numbers) will deliver blocks of direct inward dial calls already converted to Session Initiation Protocol (SIP) or common VoIP formats.

List of mobile telephone prefixes by country

The telecommunication administrations in many countries assign specific telephone number prefixes to mobile phones within their telephone numbering plan, however some do not. The North American Numbering Plan Administration (NANPA) in the United States and its territories, Canada, and much of the Caribbean, uses normal geographic area codes for the mobile services so that a mobile telephone number is not easily recognized. International Networks (country code), allocated the +882 and +883 codes. List of country calling codes. Mobile phone. List of international call prefixes. Telephone numbering plan.

List of dialling codes in the United Kingdom

Dialling codesDialling code01439
This is a list of telephone dialling codes in the United Kingdom. The national telephone numbering plan is maintained by Ofcom, an independent regulator and competition authority for the UK communications industries. This list is based on the official standard, but includes defunct codes and historical changes, including the derivation of the two letter identities, in cases where known. The United Kingdom adopts an open telephone numbering plan for its public switched telephone network. Dialling codes do not correspond to specific political boundaries.

List of telephone exchanges in London

170 telephone exchanges
As the telephone system was modernised and liberalised with multiple telephone companies, and numbers became portable the rigid correspondence of numeric codes to exchanges was relaxed, but even today it is likely that a (7)387 number, for example, is located in the Euston area. Lists of numbers allocated to BT exchanges in the UK, including London, are available online, and enable the exchange associated with a given number to be found, if applicable. Locations of exchanges, given a postcode in their catchment area, are also documented. NOTE: The United Kingdom adopts an open dialling plan for area codes within its public switched telephone network.

Area codes 416, 647, and 437

416416, 647416, 647, 437
Nonetheless, the GTA's rapid growth and the proliferation of cell phones, fax machines, and pagers made it obvious that the Golden Horseshoe needed another area code. In 1993, the 416 territory was cut back to just Metro Toronto (York, East York, North York, Etobicoke, Scarborough and Old Toronto), while area code 905 was assigned to most of Toronto's suburbs; it almost completely surrounds 416. The split began on October 13, 1993; permissive dialing of 416 continued throughout the Golden Horseshoe until January 1, 1994.

List of dialling codes in Brazil

Area/distance codeArea code63
Country Code: +55 International Call Prefix: 00 then Carrier Code Trunk Prefix: 0 then Carrier Code This page contains a list of area codes in Brazil for telephone dialing. The area codes are distributed geographically, citing the main cities in each area. Local phone numbers in Brazil observe an eight-digit pattern (nnnn-nnnn) for landlines and nine digits (nnnnn-nnnn) for mobile phones. Mobile numbers share the same geographic area codes as landlines, but the first digit differentiates them. Landline numbers start with digits 2 through 5. Initial digits 6 through 9 are reserved for mobile numbers, but as of 2017 all mobile numbers in Brazil start with the digit 9.

Demarcation point

DanishDanessubscriber premises
Part 68) to allow safe connection of third-party telephone customer-premises equipment and wiring to the Public Switched Telephone Network (PSTN). The modern demarcation point is the network interface device (NID) or intelligent network interface device (INID) also known as a "smartjack". The NID is the telco's property. The NID may be outdoors (typically, mounted on the building exterior in a weatherproof box) or indoors. The NID is usually placed for easy access by a technician.

International rankings of Iran

International rankings of Iran in science and technologyInternational Rankings of Iran in EconomyInternational Rankings of Iran in Transport
The following are international rankings for Iran: Iran-US communications will prove to be at the best level of international trade and export exports in the world

Telephone numbers in Brazil

+55Area codeBrazil
Outbound international calls use a 00 trunk prefix, followed by the carrier selection code (same as in domestic long-distance calls) and the international telephone number. So, to call the international telephone number +cc-aa-nnnn-nnnn (where cc is the country code and aa the area code), one would dial 00-xx-cc-aa-nnnn-nnnn, where xx is the carrier selection code. Since international telephone numbers can have up to 15 digits, the maximum number of digits to be dialed is 19. For example, to call the number 555-0123 in Washington, D.C. (area code 202), United States (country code 1), using TIM as the chosen carrier (selection code 41), one would dial 00 41 1 202 555 0123.

Call forwarding

forwardingGSM forwarding standard features codescall forwarding (busy and no answer)
Call forwarding, or call diversion, is a telephony feature of some telephone switching systems which redirects a telephone call to another destination, which may be, for example, a mobile or another telephone number where the desired called party is available. Call forwarding was invented by Ernest J. Bonanno. In North America, the forwarded line usually rings once to remind the customer using call forwarding that the call is being redirected. More consistently, the forwarded line indicates its condition by stutter dial tone.