Public switched telephone network

PSTNpublic telephone networktelephone networktelephone networkspublic telephone systemtelephonetelephone systemvoice telephone systemswirecircuit-switched telephone network
The public switched telephone network (PSTN) is the aggregate of the world's circuit-switched telephone networks that are operated by national, regional, or local telephony operators, providing infrastructure and services for public telecommunication.wikipedia
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Telephone

phonetelephonesLocal Telephone Service
The public switched telephone network (PSTN) is the aggregate of the world's circuit-switched telephone networks that are operated by national, regional, or local telephony operators, providing infrastructure and services for public telecommunication.
These exchanges were soon connected together, eventually forming an automated, worldwide public switched telephone network.

Telephony

digital telephonytelephonedigital
The public switched telephone network (PSTN) is the aggregate of the world's circuit-switched telephone networks that are operated by national, regional, or local telephony operators, providing infrastructure and services for public telecommunication.
Most of the exchanges in the world are interconnected through a system of larger switching systems, forming the public switched telephone network (PSTN).

Cellular network

cellularmobile networkcellular networks
The PSTN consists of telephone lines, fiber optic cables, microwave transmission links, cellular networks, communications satellites, and undersea telephone cables, all interconnected by switching centers, thus allowing most telephones to communicate with each other.
This allows mobile phones and mobile computing devices to be connected to the public switched telephone network and public Internet.

Mobile phone

cell phonemobile phonesmobile
Originally a network of fixed-line analog telephone systems, the PSTN is now almost entirely digital in its core network and includes mobile and other networks, as well as fixed telephones.
The radio frequency link establishes a connection to the switching systems of a mobile phone operator, which provides access to the public switched telephone network (PSTN).

Telephone line

phone linelinetelephone cable
The PSTN consists of telephone lines, fiber optic cables, microwave transmission links, cellular networks, communications satellites, and undersea telephone cables, all interconnected by switching centers, thus allowing most telephones to communicate with each other.
Telephone overhead lines are connected to the public switched telephone network.

Telephone numbering plan

Area codeTelephone codearea codes
The combination of the interconnected networks and the single numbering plan allow telephones around the world to dial each other.
Telephone numbering plans are defined in each of administrative regions of the public switched telephone network (PSTN) and they are also present in private telephone networks.

E.164

E.163e164.arpae164.org
The E.163 and E.164 standards provide a single global address space for telephone numbers.
E.164 is an international standard (ITU-T Recommendation), titled The international public telecommunication numbering plan, that defines a numbering plan for the worldwide public switched telephone network (PSTN) and some other data networks.

Telephone exchange

exchangescentral officeexchange
The PSTN consists of telephone lines, fiber optic cables, microwave transmission links, cellular networks, communications satellites, and undersea telephone cables, all interconnected by switching centers, thus allowing most telephones to communicate with each other.
A telephone exchange or telephone switch is a telecommunications system used in the public switched telephone network or in large enterprises.

Backbone network

core networkbackbonenetwork backbone
Originally a network of fixed-line analog telephone systems, the PSTN is now almost entirely digital in its core network and includes mobile and other networks, as well as fixed telephones.
One of the main functions was to route telephone calls across the PSTN.

Signaling (telecommunications)

signalsignalingout-of-band signaling
Bells were soon added to stations for signaling, so an attendant no longer needed to wait for the whistle.
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.

Signalling System No. 7

SS7Signaling System 7Signalling System 7
Later, more sophisticated address signaling, including multi-frequency signaling methods, enabled direct-dialed long distance calls by subscribers, culminating in the Signalling System 7 (SS7) network that controlled calls between most exchanges by the end of the 20th century.
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).

Telephone call

callphone callphone calls
Alerting another user of the desire to establish a telephone call was accomplished by whistling loudly into the transmitter until the other party heard the alert.
Calls may be placed through a public network (such as the Public Switched Telephone Network) provided by a commercial telephone company or a private network called a PBX.

Broadband Integrated Services Digital Network

B-ISDNBroadband ISDNBroadband ISDNs
In the 1980s, the industry began planning for digital services assuming they would follow much the same pattern as voice services, and conceived end-to-end circuit-switched services, known as the Broadband Integrated Services Digital Network (B-ISDN).
In the 1980s, the telecommunications industry expected that digital services would follow much the same pattern as voice services did on the public switched telephone network, and conceived an end-to-end circuit switched services, known as Broadband Integrated Services Digital Network (B-ISDN).

Integrated Services Digital Network

ISDN ISDNISDN30
However, digital technologies such as DSL, ISDN, FTTx, and cable modems have become more common in this portion of the network.
Integrated Services Digital Network (ISDN) is a set of communication standards for simultaneous digital transmission of voice, video, data, and other network services over the traditional circuits of the public switched telephone network.

Communications satellite

satellite communicationssatellitecommunication satellite
The PSTN consists of telephone lines, fiber optic cables, microwave transmission links, cellular networks, communications satellites, and undersea telephone cables, all interconnected by switching centers, thus allowing most telephones to communicate with each other.
The fixed Public Switched Telephone Network relays telephone calls from land line telephones to an earth station, where they are then transmitted to a geostationary satellite.

Agner Krarup Erlang

A. K. ErlangA.K. ErlangErlang
The work of A. K. Erlang established the mathematical foundations of methods required to determine the capacity requirements and configuration of equipment and the number of personnel required to deliver a specific level of service.
By the time of his relatively early death at the age of 51, Erlang had created the field of telephone networks analysis.

Teletraffic engineering

traffic engineeringTeletraffic engineering in broadband networksEFCI
The growth of the PSTN meant that teletraffic engineering techniques needed to be deployed to deliver quality of service (QoS) guarantees for the users.
The measurement of traffic in a public switched telephone network (PSTN) allows network operators to determine and maintain the quality of service (QoS) and in particular the grade of service (GoS) that they promise their subscribers.

ITU-T

CCITTITU Telecommunication Standardization SectorTelecommunication Standardization Sector
The technical operation of the PSTN adheres to the standards created by the ITU-T.

Business telephone system

PBXprivate branch exchangePABX
There are also private networks run by large companies which are linked to the PSTN only through limited gateways, such as a large private branch exchange (PBX).
Early electronic key systems used dedicated handsets which displayed and allowed access to all connected PSTN lines and stations.

Multi-frequency signaling

multi-frequencyMFmultifrequency
Later, more sophisticated address signaling, including multi-frequency signaling methods, enabled direct-dialed long distance calls by subscribers, culminating in the Signalling System 7 (SS7) network that controlled calls between most exchanges by the end of the 20th century.
In-band signaling fell into disfavor in the public switched telephone network (PSTN) as electronic switching systems displaced electro-mechanical switching systems, but legacy offices may still exist, such as in Russia and Italy, that are still using some electromechanical and other legacy switching equipment in the PSTN.

Routing in the PSTN

routingDynamic Alternative Routingalternate route
The call is switched using a call set up protocol (usually ISUP) between the telephone exchanges under an overall routing strategy.
Routing in the PSTN is the process used to route telephone calls across the public switched telephone network.

Cable modem

cablecable modemscable internet
However, digital technologies such as DSL, ISDN, FTTx, and cable modems have become more common in this portion of the network.
The earliest systems used the public switched telephone network (PSTN) for the return path since very few cable systems were bi-directional.

ISDN User Part

ISUPRelease (ISUP)
The call is switched using a call set up protocol (usually ISUP) between the telephone exchanges under an overall routing strategy.
The ISDN (Integrated Services Digital Network) User Part or ISUP is part of Signaling System No. 7 (SS7), which is used to set up telephone calls in the public switched telephone network (PSTN).

Digital subscriber line

DSLxDSLDigital Subscriber Line (DSL)
However, digital technologies such as DSL, ISDN, FTTx, and cable modems have become more common in this portion of the network.
A naked DSL (also known as standalone or dry loop DSL) is a way of providing DSL services without a PSTN (analogue telephony) service.

Quality of service

QoSquality-of-serviceQuality of Service (QoS)
The growth of the PSTN meant that teletraffic engineering techniques needed to be deployed to deliver quality of service (QoS) guarantees for the users.
Mobile cellular service providers may offer mobile QoS to customers just as the fixed line PSTN services providers and Internet Service Providers (ISP) may offer QoS.