Jaringan telepon umum: Béda antarrépisi

{{tarjamahkeun|Inggris}}

 

The PSTN was the earliest example of [[traffic engineering (telecommunications)|traffic engineering]] to deliver [[Quality of Service]] (QoS) guarantees. [[Agner Krarup Erlang|A.K. Erlang]] (1878–1929) is credited with establishing the mathematical foundations of methods required to determine the amount and configuration of equipment and the number of personnel required to deliver a specific level of service.

 

There are a number of large private telephone networks which are not linked to the PSTN, usually for military purposes. There are also private networks run by large companies which are linked to the PSTN only through limited [[Gateway (telecommunications)|gateways]], like a large [[private branch exchange]] (PBX).

 

The first telephones had no network but were in private use, wired together in pairs. Users who wanted to talk to different people had as many telephones as necessary for the purpose. A user who wished to speak, whistled into the transmitter until the other party heard. Soon, however, a bell was added for signalling, and then a switchhook, and telephones took advantage of the exchange principle already employed in telegraph networks. Each telephone was wired to a local [[telephone exchange]], and the exchanges were wired together with [[trunking|trunks]]. Networks were connected together in a hierarchical manner until they spanned cities, countries, continents and oceans. This was the beginning of the PSTN, though the term was unknown for many decades.

 

Automation introduced [[pulse dial]]ing between the phone and the exchange, and then among exchanges, followed by more sophisticated address signaling including [[multi-frequency]], culminating in the [[SS7]] network that connected most exchanges by the end of the 20th century.

 

{{main|telephone exchange}}

 

 

The basic digital circuit in the PSTN is a 64-[[Kbit/s|kilobits-per-second]] channel, originally designed by [[Bell Labs]], called Digital Signal 0 ([[DS0]]). To carry a typical phone call from a [[calling party]] to a [[called party]], the audio sound is digitized at an 8 kHz sample rate using 8-bit [[pulse code modulation]] (PCM). The call is then transmitted from one end to another via telephone exchanges. The call is [[circuit switching|switched]] using a [[Signaling (telecommunication)|signaling]] [[protocol (computing)|protocol]] ([[SS7]]) between the telephone exchanges under an overall [[routing in the PSTN|routing strategy]].

 

 

The timeslots are conveyed from the initial multiplexer to the exchange over a set of equipment collectively known as the [[access network]]. The access network and inter-exchange transport of the PSTN use [[synchronization|synchronous]] optical transmission ([[SONET]] and [[Synchronous digital hierarchy|SDH]]) technology, although some parts still use the older [[PDH]] technology.

Within the access network, there are a number of [[reference point]]s defined. Most of these are of interest mainly to [[ISDN]] but one – the [[V reference point]] – is of more general interest. This is the reference point between a primary multiplexer and an exchange. The protocols at this reference point were standardised in [[ETSI]] areas as the [[V5 interface]].

 

 

 

 

[[ar:الشبكة العامة لتحويل الهاتف]]

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[[ca:Xarxa Telefònica Commutada]]

[[da:Public Switched Telephone Network]]

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[[en:Public switched telephone network]]

[[es:Red Telefónica Conmutada]]

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[[fr:Réseau téléphonique commuté]]