{"industry":{"id":"ff619d7c-d7d7-485e-a05a-53fba07f33ed","slug":"telecommunications","label":"Telecommunications","description":"Business voice, fiber, UCaaS, and network services"},"topic":{"slug":"pstn","label":"PSTN","description":"The public switched telephone network: how it works, POTS retirement, and the move to VoIP.","schemaKind":null},"answer":{"id":"64a64f8a-a710-4a70-b21b-292c1eb247b6","slug":"what-is-the-pstn-public-switched-telephone-network","question":"What is the PSTN (Public Switched Telephone Network)?","answerMarkdown":"The PSTN, or public switched telephone network, is the combined telephone networks of the world's carriers, connected so that a number on one can be dialed from another. No single company owns it. Landline and mobile carriers both belong to it, and a service that gives you an ordinary phone number reaches it through a carrier. It began as a network of copper lines and circuit switches, and parts of it now run on IP.","answerText":"The PSTN, or public switched telephone network, is the combined telephone networks of the world's carriers, connected so that a number on one can be dialed from another. No single company owns it. Landline and mobile carriers both belong to it, and a service that gives you an ordinary phone number reaches it through a carrier. It began as a network of copper lines and circuit switches, and parts of it now run on IP.","answerHtml":"

The PSTN, or public switched telephone network, is the combined telephone networks of the world's carriers, connected so that a number on one can be dialed from another. No single company owns it. Landline and mobile carriers both belong to it, and a service that gives you an ordinary phone number reaches it through a carrier. It began as a network of copper lines and circuit switches, and parts of it now run on IP.

\n","summary":"The PSTN is the combined telephone networks of the world's carriers, connected so that a number on one can be dialed from another. No single company owns it. Landline and mobile carriers both belong to it, and a shared numbering system holds it together. It began with copper lines and circuit switches, and parts of it now run on IP.","publishedAt":"2026-09-23T15:17:01.345","verifiedAt":"2026-07-18T00:00:00","editorialStatus":"APPROVED","lastReviewedAt":"2026-10-10T03:21:15.959","nextReviewDueAt":"2026-10-18T00:00:00","templateVersion":"v2","aliases":["What does PSTN stand for?","What is the public switched telephone network?","PSTN meaning","How does the PSTN work?","What is a landline network?","What is the traditional telephone network?","Circuit-switched telephone network explained","PSTN vs VoIP","What is POTS?","Is the PSTN being switched off?","What is the difference between PSTN and VoIP?","How are phone calls routed on the PSTN?"],"confidenceScore":93,"confidenceLabel":"High","canonicalUrl":null},"contributor":{"id":"ec39deab-44fe-48d8-9029-fefe993ab85a","slug":"answer-stack","displayName":"AnswerStack","websiteUrl":null},"contributorOrganizationProfile":null,"contributorPerson":null,"sections":[{"id":"8e26bed2-9b98-4e8c-a9c8-7e9b2865484e","sectionKey":"what_the_name_says","sectionType":"markdown_section","heading":"What the name says","introMarkdown":"Public means the network is open to anyone who subscribes and connects them to subscribers on other carriers. [A company's internal phone system](https://www.answerstack.io/q/what-is-the-difference-between-pstn-and-pbx) is private by comparison, even though it links to the public network.\n\nSwitched means the network makes connections on demand. You don't have a fixed wire to each person you might call. You dial a number, and the network finds a route to it for the length of the call. Telephone means it was built for voice, though fax machines, alarm panels and dial-up modems were later designed to use it too.\n\nUS rules define it along the same lines. [47 CFR 20.3](https://www.law.cornell.edu/cfr/text/47/20.3) describes the public switched network as any common carrier switched network, by wire or radio, that uses the North American Numbering Plan. It names local exchange carriers, long-distance carriers and mobile service providers. That is a US rule, and other countries write their own. It does show why treating the PSTN as another word for landlines gives the wrong picture, because mobile networks sit inside the definition.","introHtml":"

Public means the network is open to anyone who subscribes and connects them to subscribers on other carriers. A company's internal phone system is private by comparison, even though it links to the public network.

\n

Switched means the network makes connections on demand. You don't have a fixed wire to each person you might call. You dial a number, and the network finds a route to it for the length of the call. Telephone means it was built for voice, though fax machines, alarm panels and dial-up modems were later designed to use it too.

\n

US rules define it along the same lines. 47 CFR 20.3 describes the public switched network as any common carrier switched network, by wire or radio, that uses the North American Numbering Plan. It names local exchange carriers, long-distance carriers and mobile service providers. That is a US rule, and other countries write their own. It does show why treating the PSTN as another word for landlines gives the wrong picture, because mobile networks sit inside the definition.

\n","outroMarkdown":null,"outroHtml":null,"contentJson":{},"configJson":{},"noteMarkdown":null,"noteHtml":null,"sortOrder":10},{"id":"5ddf878a-daab-4dd8-91ea-b40ce16e83c0","sectionKey":"phone_numbers_hold_it_together","sectionType":"markdown_section","heading":"Phone numbers hold it together","introMarkdown":"A shared numbering system is what lets many separate networks behave as one. Carriers draw their numbers from a shared plan, and the plan gives every network a common way to address a call.\n\nThe United States shares its plan with 19 other countries. [NANPA](https://www.nanpa.com/about), the plan's administrator, describes the North American Numbering Plan as serving 20 countries under country code 1. Its numbers have ten digits: a three-digit area code followed by a seven-digit local number. NANPA assigns the numbering resources and follows the rules that regulators set, and each member country keeps authority over its own numbers. The plan conforms with ITU Recommendation E.164, which NANPA calls the international standard for telephone numbering plans. That common standard is what lets a call be addressed from one country's plan to another's.\n\nA number is an address on the network. It doesn't belong to a particular wire or device, and that is easiest to see when a line is replaced. Atlantech Online, a business phone and fiber provider, replaces copper phone lines with a managed appliance that connects over broadband and 4G LTE. In its [description of the cutover](https://www.atlantech.net/solutions/voice/pots-replacement), the existing numbers for the fire panel, elevator, alarm panel and fax lines are ported to the new service. Atlantech says the central monitoring station keeps receiving calls from the same caller ID. The analog line has been replaced, and the rest of the public network still finds each device at the same number.","introHtml":"

A shared numbering system is what lets many separate networks behave as one. Carriers draw their numbers from a shared plan, and the plan gives every network a common way to address a call.

\n

The United States shares its plan with 19 other countries. NANPA, the plan's administrator, describes the North American Numbering Plan as serving 20 countries under country code 1. Its numbers have ten digits: a three-digit area code followed by a seven-digit local number. NANPA assigns the numbering resources and follows the rules that regulators set, and each member country keeps authority over its own numbers. The plan conforms with ITU Recommendation E.164, which NANPA calls the international standard for telephone numbering plans. That common standard is what lets a call be addressed from one country's plan to another's.

\n

A number is an address on the network. It doesn't belong to a particular wire or device, and that is easiest to see when a line is replaced. Atlantech Online, a business phone and fiber provider, replaces copper phone lines with a managed appliance that connects over broadband and 4G LTE. In its description of the cutover, the existing numbers for the fire panel, elevator, alarm panel and fax lines are ported to the new service. Atlantech says the central monitoring station keeps receiving calls from the same caller ID. The analog line has been replaced, and the rest of the public network still finds each device at the same number.

\n","outroMarkdown":null,"outroHtml":null,"contentJson":{},"configJson":{},"noteMarkdown":null,"noteHtml":null,"sortOrder":20},{"id":"672350d3-7f8b-411b-ac51-e4f37af8acaf","sectionKey":"what_happens_when_you_dial","sectionType":"markdown_section","heading":"What happens when you dial","introMarkdown":"[A call on the PSTN](https://www.answerstack.io/q/how-does-the-pstn-work) has two parts. Setup comes first: the carriers' equipment exchanges signaling messages, and the dialed number in them routes the call toward its destination. Once the far phone answers, the two ends share a voice path for the rest of the call.\n\nOn older parts of the network that path is a reserved digital circuit. On newer parts the voice travels as [IP packets](https://www.answerstack.io/q/what-is-the-difference-between-pstn-and-voip). The FCC's [2025 notice on IP interconnection](https://www.federalregister.gov/documents/2025/11/26/2025-21324/advancing-ip-interconnection) describes IP voice networks that carry calls from end to end, and a handoff through a media gateway wherever a call has to cross circuit equipment. The caller sees none of this.","introHtml":"

A call on the PSTN has two parts. Setup comes first: the carriers' equipment exchanges signaling messages, and the dialed number in them routes the call toward its destination. Once the far phone answers, the two ends share a voice path for the rest of the call.

\n

On older parts of the network that path is a reserved digital circuit. On newer parts the voice travels as IP packets. The FCC's 2025 notice on IP interconnection describes IP voice networks that carry calls from end to end, and a handoff through a media gateway wherever a call has to cross circuit equipment. The caller sees none of this.

\n","outroMarkdown":null,"outroHtml":null,"contentJson":{},"configJson":{},"noteMarkdown":null,"noteHtml":null,"sortOrder":30},{"id":"bb5e04cc-979b-41bd-9771-20c699aeca73","sectionKey":"how_you_get_onto_it","sectionType":"markdown_section","heading":"How you get onto it","introMarkdown":"You reach the PSTN by buying access from a carrier, and that access now comes in several forms.\n\nThe original form is [the analog line on a copper pair, known as POTS](https://www.answerstack.io/q/what-is-the-difference-between-pstn-and-pots). A mobile subscription is another, and businesses have more choices. Atlantech's [business phone service](https://www.atlantech.net/solutions/voice/phone) offers a cloud PBX, or delivery to a PBX the customer already owns over SIP, PRI or analog lines.\n\nMicrosoft Teams needs the same access for calls to public phone numbers. Microsoft's [Teams Phone overview](https://learn.microsoft.com/en-us/microsoftteams/what-is-phone-system-in-office-365) says a PSTN connection is separate from the Teams Phone license. The connection is what provides phone numbers and access to domestic, international and emergency calling.\n\nIn each case the carrier supplies the same two things, a public number and a route to other public numbers.","introHtml":"

You reach the PSTN by buying access from a carrier, and that access now comes in several forms.

\n

The original form is the analog line on a copper pair, known as POTS. A mobile subscription is another, and businesses have more choices. Atlantech's business phone service offers a cloud PBX, or delivery to a PBX the customer already owns over SIP, PRI or analog lines.

\n

Microsoft Teams needs the same access for calls to public phone numbers. Microsoft's Teams Phone overview says a PSTN connection is separate from the Teams Phone license. The connection is what provides phone numbers and access to domestic, international and emergency calling.

\n

In each case the carrier supplies the same two things, a public number and a route to other public numbers.

\n","outroMarkdown":null,"outroHtml":null,"contentJson":{},"configJson":{},"noteMarkdown":null,"noteHtml":null,"sortOrder":40},{"id":"60c97512-07d8-4a9b-b822-fd484dd10319","sectionKey":"terms_confused_with_the_pstn","sectionType":"table_section","heading":"Terms often confused with the PSTN","introMarkdown":null,"introHtml":null,"outroMarkdown":null,"outroHtml":null,"contentJson":{"rows":[{"cells":["POTS","A single analog phone line on a copper pair","One way to connect to it"]},{"cells":["PBX","A private phone system that handles a company's extensions","Connects to it through carrier lines or trunks"]},{"cells":["VoIP","Voice carried as IP packets","Used by services that connect to it and by carriers inside it"]},{"cells":["SIP trunk","An IP connection between a phone system and a carrier","Carries a company's calls to and from it"]}],"columns":["Term","What it is","How it relates to the PSTN"]},"configJson":{},"noteMarkdown":null,"noteHtml":null,"sortOrder":50},{"id":"cac42e16-5568-4fe1-aa61-b07dfcf82809","sectionKey":"what_pstn_retirement_refers_to","sectionType":"markdown_section","heading":"What \"PSTN retirement\" refers to","introMarkdown":"In the UK, PSTN is also the name of a legacy analog network. Openreach, a UK network operator, [confirmed in September 2026](https://www.openreach.com/news/openreach-to-protect-broadband--connections-as-pstn-closure---approaches/) that it closes on January 31, 2027, and estimated that about 1.2 million lines were still on it. What closes is old equipment and old lines.\n\nCustomers can keep a landline by moving to a replacement service. The UK government's [guidance on the change](https://www.gov.uk/guidance/uk-transition-from-analogue-to-digital-landlines) says providers are upgrading landlines to digital technology that uses an internet connection, and that nobody has to lose their landline service because of it.\n\nIn the wider sense used here, the PSTN carries on while carriers replace the technology inside it. Phone numbers and the connections between carriers stay in place as the equipment changes.","introHtml":"

In the UK, PSTN is also the name of a legacy analog network. Openreach, a UK network operator, confirmed in September 2026 that it closes on January 31, 2027, and estimated that about 1.2 million lines were still on it. What closes is old equipment and old lines.

\n

Customers can keep a landline by moving to a replacement service. The UK government's guidance on the change says providers are upgrading landlines to digital technology that uses an internet connection, and that nobody has to lose their landline service because of it.

\n

In the wider sense used here, the PSTN carries on while carriers replace the technology inside it. Phone numbers and the connections between carriers stay in place as the equipment changes.

\n","outroMarkdown":null,"outroHtml":null,"contentJson":{},"configJson":{},"noteMarkdown":null,"noteHtml":null,"sortOrder":60}],"citations":[{"title":"Public switched telephone network","url":"https://en.wikipedia.org/wiki/Public_switched_telephone_network","excerpt":"The public switched telephone network (PSTN) is the aggregate of the world's telephone networks that are operated by national, regional, or local telephony operators.","quoteText":null,"sourceRole":"INDEPENDENT","verifiedAt":"2026-07-18T00:00:00","supportsText":"Definition of the PSTN as the aggregate of operator-run telephone networks; structure of local loops, exchanges, trunks, and the switching hierarchy; digital core with PCM, DS0, SONET/SDH; SS7 controlling calls between exchanges; ITU standards","domain":"en.wikipedia.org","publisherName":"Wikipedia"},{"title":"PSTN (public switched telephone network)","url":"https://www.techtarget.com/searchnetworking/definition/PSTN","excerpt":"PSTN (public switched telephone network) is the world's collection of interconnected voice-oriented public telephone networks via traditional circuit-switched networks.","quoteText":null,"sourceRole":"INDEPENDENT","verifiedAt":"2026-07-18T00:00:00","supportsText":"PSTN as interconnected circuit-switched networks; dedicated path per call for the call duration; hierarchical local, trunk, and main exchanges; providers transitioning to all-IP; comparison with VoIP","domain":"techtarget.com","publisherName":"Informa TechTarget"},{"title":"ITU-T G.711: Pulse code modulation (PCM) of voice frequencies","url":"https://www.itu.int/rec/T-REC-G.711/","excerpt":"Pulse code modulation (PCM) of voice frequencies. Status: In force.","quoteText":null,"sourceRole":"PRIMARY","verifiedAt":"2026-07-18T00:00:00","supportsText":"G.711 defines pulse code modulation encoding of voice frequencies, the baseline digital voice channel of the telephone network; in force","domain":"itu.int","publisherName":"International Telecommunication Union (ITU-T)"},{"title":"ITU-T Q.700: Introduction to CCITT Signalling System No. 7","url":"https://www.itu.int/rec/T-REC-Q.700/","excerpt":"Introduction to CCITT Signalling System No. 7","quoteText":null,"sourceRole":"PRIMARY","verifiedAt":"2026-07-18T00:00:00","supportsText":"Signalling System No. 7 (SS7) as the out-of-band signaling framework that sets up, routes, and releases PSTN calls; standardized in the Q.700 series; in force","domain":"itu.int","publisherName":"International Telecommunication Union (ITU-T)"},{"title":"ITU-T E.164: The international public telecommunication numbering plan","url":"https://www.itu.int/rec/T-REC-E.164/","excerpt":"The international public telecommunication numbering plan","quoteText":null,"sourceRole":"PRIMARY","verifiedAt":"2026-07-18T00:00:00","supportsText":"E.164 is the international public telecommunication numbering plan; maximum 15 digits; country code of one to three digits; governs numbering across the worldwide PSTN; in force, replaces E.163","domain":"itu.int","publisherName":"International Telecommunication Union (ITU-T)"},{"title":"About NANPA","url":"https://www.nanpa.com/about","excerpt":"NANPA holds overall responsibility for the neutral administration of NANP numbering resources, subject to directives from regulatory authorities in the countries that share the NANP.","quoteText":null,"sourceRole":"PRIMARY","verifiedAt":"2026-07-18T00:00:00","supportsText":"North American Numbering Plan structure: country code 1, NPA-NXX-XXXX ten-digit format, 20 participating countries and territories, neutral administration of numbering resources","domain":"nanpa.com","publisherName":"North American Numbering Plan Administrator (NANPA)"},{"title":"The Plesiochronous Digital Hierarchy","url":"https://www.technologyuk.net/telecommunications/communication-technologies/plesiochronous-digital-hierarchy.shtml","excerpt":"The digitisation of an analogue voice channel into a 64 kbps digital channel (designated as digital signalling level zero or simply DS0)","quoteText":null,"sourceRole":"INDEPENDENT","verifiedAt":"2026-07-18T00:00:00","supportsText":"DS0 is a 64 kbit/s digital voice channel from PCM; T1/DS1 carries 24 channels at 1.544 Mbit/s in North America; E1 carries 32 timeslots (30 voice) at 2.048 Mbit/s; time-division multiplexing onto trunks","domain":"technologyuk.net","publisherName":"TechnologyUK"},{"title":"Time for a big switch-up as PSTN switch-off looms","url":"https://www.openreach.com/news/time-for-a-big-switch-up-as-pstn-switch-off-looms/","excerpt":"BT Group will retire the PSTN network by 31st January 2027","quoteText":null,"sourceRole":"PRIMARY","verifiedAt":"2026-07-18T00:00:00","supportsText":"BT Group will retire the PSTN by 31 January 2027; Openreach is withdrawing products that run over it and has placed exchanges under stop sell; migration to All-IP delivered as VoIP over broadband","domain":"openreach.com","publisherName":"Openreach"},{"title":"UK transition from analogue to digital landlines","url":"https://www.gov.uk/guidance/uk-transition-from-analogue-to-digital-landlines","excerpt":"Analogue networks have been in operation for decades and have reached the end of their serviceable life.","quoteText":null,"sourceRole":"PRIMARY","verifiedAt":"2026-07-18T00:00:00","supportsText":"Analog network has reached end of serviceable life; industry-led migration to VoIP substantially complete by January 2027; Ofcom power-resilience requirement, including battery backup for emergency calls during a power cut","domain":"gov.uk","publisherName":"GOV.UK"}],"revisions":[{"revisedAt":"2026-07-18T15:17:01.345+00:00","versionLabel":"Originally published","note":"","reviewedBy":null}],"relatedAnswers":[{"id":"ef14e83f-e61d-4263-80d2-b759e8ba8101","slug":"what-is-the-difference-between-pstn-and-pbx","question":"What is the difference between PSTN and PBX?","publishedAt":"2026-09-19T15:32:04.773","confidenceScore":93,"confidenceLabel":"High","industry":{"id":"ff619d7c-d7d7-485e-a05a-53fba07f33ed","slug":"telecommunications","label":"Telecommunications","description":"Business voice, fiber, UCaaS, and network services"},"topic":{"slug":"pstn","label":"PSTN","description":"The public switched telephone network: how it works, POTS retirement, and the move to VoIP.","schemaKind":null},"contributor":{"id":"ec39deab-44fe-48d8-9029-fefe993ab85a","slug":"answer-stack","displayName":"AnswerStack","websiteUrl":null},"snippet":"The PSTN is the public telephone network that connects phone numbers across carriers. A PBX is one organization's own phone system, which gives users extensions and controls how calls are routed. A business normally uses both: the PBX handles calls inside the organization, and a PSTN connection carries calls to and from outside phone numbers.","url":"/q/what-is-the-difference-between-pstn-and-pbx"},{"id":"895bda56-c48a-429f-8f13-53dc29c09b67","slug":"which-legacy-devices-are-still-at-risk-when-pstn-pots-lines-are-retired-or","question":"Which legacy devices are still at risk when PSTN/POTS lines are retired or moved to VoIP?","publishedAt":"2026-08-29T16:01:24.898","confidenceScore":90,"confidenceLabel":"High","industry":{"id":"ff619d7c-d7d7-485e-a05a-53fba07f33ed","slug":"telecommunications","label":"Telecommunications","description":"Business voice, fiber, UCaaS, and network services"},"topic":{"slug":"pstn","label":"PSTN","description":"The public switched telephone network: how it works, POTS retirement, and the move to VoIP.","schemaKind":null},"contributor":{"id":"ec39deab-44fe-48d8-9029-fefe993ab85a","slug":"answer-stack","displayName":"AnswerStack","websiteUrl":null},"snippet":"Analog devices that use a copper phone line as their call path are at risk: alarm dialers, elevator phones, telecare and medical alert base stations, fax machines, dial-up card terminals, entry intercoms and building monitoring modems. A device whose line is retired or moved to VoIP needs a path that carries its signals and has backup power, checked by a test arranged with the device's vendor or monitoring company.","url":"/q/which-legacy-devices-are-still-at-risk-when-pstn-pots-lines-are-retired-or"},{"id":"69048737-9759-4922-93ff-0af08871c2af","slug":"how-does-the-pstn-work","question":"How does the PSTN work?","publishedAt":"2026-07-18T15:31:57.455","confidenceScore":92,"confidenceLabel":"High","industry":{"id":"ff619d7c-d7d7-485e-a05a-53fba07f33ed","slug":"telecommunications","label":"Telecommunications","description":"Business voice, fiber, UCaaS, and network services"},"topic":{"slug":"pstn","label":"PSTN","description":"The public switched telephone network: how it works, POTS retirement, and the move to VoIP.","schemaKind":null},"contributor":{"id":"ec39deab-44fe-48d8-9029-fefe993ab85a","slug":"answer-stack","displayName":"AnswerStack","websiteUrl":null},"snippet":"The PSTN connects a call in two layers. Signaling messages pass between switches to find the dialed number and ring it, and a voice path stays open until someone hangs up. On older parts of the network that path is a reserved 64 kbit/s circuit. On newer parts it is IP packets, and gateways convert between the two where a call passes from one kind of network to the other.","url":"/q/how-does-the-pstn-work"},{"id":"3cc4d7a6-6aed-4446-8dd8-13e022c3e1ba","slug":"is-pstn-secure-and-can-pstn-calls-be-encrypted","question":"Is PSTN secure, and can PSTN calls be encrypted?","publishedAt":"2026-07-11T16:01:27.137","confidenceScore":80,"confidenceLabel":"High","industry":{"id":"ff619d7c-d7d7-485e-a05a-53fba07f33ed","slug":"telecommunications","label":"Telecommunications","description":"Business voice, fiber, UCaaS, and network services"},"topic":{"slug":"pstn","label":"PSTN","description":"The public switched telephone network: how it works, POTS retirement, and the move to VoIP.","schemaKind":null},"contributor":{"id":"ec39deab-44fe-48d8-9029-fefe993ab85a","slug":"answer-stack","displayName":"AnswerStack","websiteUrl":null},"snippet":"The PSTN gives a call no end-to-end encryption. Its security rests on how each carrier on the path protects its own network, which a caller can't see. Individual legs can be encrypted, such as the IP leg between a phone or app and its provider, but each protection runs between two devices that share the keys and ends at the device that decrypts the call to pass it on. End-to-end encryption needs compatible equipment or software at both ends.","url":"/q/is-pstn-secure-and-can-pstn-calls-be-encrypted"}],"contributorStats":{"verifiedAnswers":149,"openDisputes":0},"schemaJson":{"@context":"https://schema.org","@type":"Question","name":"What is the PSTN (Public Switched Telephone Network)?","text":"What is the PSTN (Public Switched Telephone Network)?","url":"https://www.answerstack.io/q/what-is-the-pstn-public-switched-telephone-network","answerCount":1,"datePublished":"2026-09-23T15:17:01.345","about":[{"@type":"Thing","name":"PSTN"},{"@type":"Thing","name":"Telecommunications"}],"acceptedAnswer":{"@type":"Answer","text":"The PSTN, or public switched telephone network, is the combined telephone networks of the world's carriers, connected so that a number on one can be dialed from another. No single company owns it. Landline and mobile carriers both belong to it, and a service that gives you an ordinary phone number reaches it through a carrier. It began as a network of copper lines and circuit switches, and parts of it now run on IP.","url":"https://www.answerstack.io/q/what-is-the-pstn-public-switched-telephone-network","upvoteCount":0,"datePublished":"2026-09-23T15:17:01.345","dateModified":"2026-07-18T00:00:00","citation":[{"@type":"CreativeWork","name":"Public switched telephone network","url":"https://en.wikipedia.org/wiki/Public_switched_telephone_network"},{"@type":"CreativeWork","name":"PSTN (public switched telephone network)","url":"https://www.techtarget.com/searchnetworking/definition/PSTN"},{"@type":"CreativeWork","name":"ITU-T G.711: Pulse code modulation (PCM) of voice frequencies","url":"https://www.itu.int/rec/T-REC-G.711/"},{"@type":"CreativeWork","name":"ITU-T Q.700: Introduction to CCITT Signalling System No. 7","url":"https://www.itu.int/rec/T-REC-Q.700/"},{"@type":"CreativeWork","name":"ITU-T E.164: The international public telecommunication numbering plan","url":"https://www.itu.int/rec/T-REC-E.164/"},{"@type":"CreativeWork","name":"About NANPA","url":"https://www.nanpa.com/about"},{"@type":"CreativeWork","name":"The Plesiochronous Digital Hierarchy","url":"https://www.technologyuk.net/telecommunications/communication-technologies/plesiochronous-digital-hierarchy.shtml"},{"@type":"CreativeWork","name":"Time for a big switch-up as PSTN switch-off looms","url":"https://www.openreach.com/news/time-for-a-big-switch-up-as-pstn-switch-off-looms/"},{"@type":"CreativeWork","name":"UK transition from analogue to digital landlines","url":"https://www.gov.uk/guidance/uk-transition-from-analogue-to-digital-landlines"}]}}}