Digital subscriber line

DSLxDSLDigital Subscriber Line (DSL)
A naked DSL (also known as standalone or dry loop DSL) is a way of providing DSL services without a PSTN (analogue telephony) service. It is useful when the customer does not need the traditional telephony voice service because voice service is received either on top of the DSL services (usually VoIP) or through another network (mobile telephony). It is also commonly called a UNE (for unbundled network element) in the United States; in Australia it is known as a ULL (unconditioned local loop); in Belgium it is known as "raw copper" and in the UK it is known as Single Order GEA (SoGEA).

Local loop

subscriber lineloopsubscriber loop
In telephony, the local loop (also referred to as a local tail, subscriber line, or in the aggregate as the last mile) is the physical link or circuit that connects from the demarcation point of the customer premises to the edge of the common carrier or telecommunications service provider's network. At the edge of the carrier access network in a traditional public telephone network, the local loop terminates in a circuit switch housed in an incumbent local exchange carrier or telephone exchange. Traditionally, the local loop was an electrical circuit in the form of a single pair of conductors from the telephone on the customer's premises to the local telephone exchange.

Telephone line

phone linelinetelephone lines
A telephone line or telephone circuit (or just line or circuit within the industry) is a single-user circuit on a telephone communication system. This is the physical wire or other signaling medium connecting the user's telephone apparatus to the telecommunications network, and usually also implies a single telephone number for billing purposes reserved for that user. Telephone lines are used to deliver landline telephone service and Digital subscriber line (DSL) phone cable service to the premises. Telephone overhead lines are connected to the public switched telephone network.

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.

Pulse-code modulation

For example, in telephony, the usable voice frequency band ranges from approximately 300 Hz to 3400 Hz. For effective reconstruction of the voice signal, telephony applications therefore typically uses an 8000 Hz sampling frequency which is more than twice the highest usable voice frequency. Regardless, there are potential sources of impairment implicit in any PCM system: In conventional PCM, the analog signal may be processed (e.g., by amplitude compression) before being digitized. Once the signal is digitized, the PCM signal is usually subjected to further processing (e.g., digital data compression). PCM with linear quantization is known as Linear PCM (LPCM).

SIM card

SIMnano-SIMSIM cards
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.

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.

Disruptive innovation

disruptive technologydisruptive technologiesdisruption
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.


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."


smartphonessmart phonesmart phones
Smartphones (contraction of smart and telephone) are a class of mobile phones and of multi-purpose mobile computing devices. They are distinguished from feature phones by their stronger hardware capabilities and extensive mobile operating systems, which facilitate wider software, internet (including web browsing over mobile broadband), and multimedia functionality (including music, video, cameras, and gaming), alongside core phone functions such as voice calls and text messaging.

GSM services

servicesmobile data serviceGSM
The systems that monitor and provide the prepaid services are not part of the GSM standard services, but instead an example of intelligent network services that a mobile phone operator may decide to implement in addition to the standard GSM ones. When someone places a call to a mobile phone, they dial the telephone number (also called a MSISDN) associated with the phone user and the call is routed to the mobile phone operator's Gateway Mobile Switching Centre. The Gateway MSC, as the name suggests, acts as the "entrance" from exterior portions of the Public Switched Telephone Network onto the provider's network.

Mobile telephony

mobile communicationmobile telecommunicationsmobile communications
Mobile telephony is the provision of telephone services to phones which may move around freely rather than stay fixed in one location. Mobile phones connect to a terrestrial cellular network of base stations (cell sites), whereas satellite phones connect to orbiting satellites. Both networks are interconnected to the public switched telephone network (PSTN) to allow any phone in the world to be dialed. In 2010 there were estimated to be five billion mobile cellular subscriptions in the world.


played it for a 911 operatora false report from an anonymous caller claiming that there was a hostage situation in Hogg's family home.false report about a stabbing
Caller ID spoofing, social engineering, TTY, prank calls and phone phreaking techniques may be variously combined by swatting perpetrators. 911 systems (including computer telephony systems and human operators) have been tricked by calls placed from cities hundreds of miles away from the location of the purported call, or even from other countries. The caller typically places a 911 call using a spoofed phone number (so as to hide the fraudulent caller's real location) with the goal of tricking emergency authorities into responding with a SWAT team to a fabricated emergency.

Internet access

broadband internetbroadbandbroadband Internet access
Mobile broadband is the marketing term for wireless Internet access delivered through mobile phone towers to computers, mobile phones (called "cell phones" in North America and South Africa, and "hand phones" in Asia), and other digital devices using portable modems. Some mobile services allow more than one device to be connected to the Internet using a single cellular connection using a process called tethering. The modem may be built into laptop computers, tablets, mobile phones, and other devices, added to some devices using PC cards, USB modems, and USB sticks or dongles, or separate wireless modems can be used.

Telephone numbers in the United Kingdom

+44dialling code0141
Telephone numbers in the United Kingdom are administered by the UK government's Office of Communications (Ofcom). For this purpose Ofcom established a telephone numbering plan, known as the National Telephone Numbering Plan, which is the system for assigning telephone numbers to subscriber stations. The numbers are of variable length. Local numbers are supported from land-lines, or numbers can be dialled with a '0'-lead prefix that denotes either a geographical region or another service. Cell phone numbers have their own prefixes which are not geographical and are completely portable between providers.

Trunk prefix

trunk code8city or region
However, because the world's telephone systems are "intelligent" enough to "know" from where the call has been originated, to where the call is directed and as to how it is to be charged, if the full international number is used, then this full international number may be dialed from any telephone anywhere. This is particularly important for users of mobile phones. Such users are strongly advised to store all numbers in their phones in the form of "+ (Country Code) (Area Code) (Local Number)", no matter where they live.

Network switching subsystem

HLRMSCHome Location Register
Network switching subsystem (NSS) (or GSM core network) is the component of a GSM system that carries out call out and mobility management functions for mobile phones roaming on the network of base stations. It is owned and deployed by mobile phone operators and allows mobile devices to communicate with each other and telephones in the wider public switched telephone network (PSTN). The architecture contains specific features and functions which are needed because the phones are not fixed in one location. The NSS originally consisted of the circuit-switched core network, used for traditional GSM services such as voice calls, SMS, and circuit switched data calls.

Operator Toll Dialing

Nationwide Operator Toll Dialing
Operator Toll Dialing was a project and method used by the Bell System in the USA and Canada to automate the switching and billing of long distance calls in the public switched telephone network (PSTN). The program was initiated by 1945, at which time ca. 5% of the 2.7 million toll board calls per day were handled by this method. Operator Toll Dialing eliminated the need for intermediate and inward operators to complete toll calls to distant central offices. Initially this system involved step-by-step routings to set up each circuit, but later was improved by the development of area codes with machine translation which helped to standardize dialing across the network.