POTS is a kind of phone line, and the PSTN is the public network that line connects you to. POTS stands for plain old telephone service: one analog voice line that a telephone company delivers over a pair of copper wires. The PSTN, the public switched telephone network, is the networks of the telephone carriers, connected so that a number on one can be dialed from another. A POTS line is one way onto the PSTN. A mobile phone, a SIP trunk and a cloud phone service are others.
\n","summary":"POTS is a kind of phone line and the PSTN is the public network that line connects you to. A POTS line is one analog voice line on a copper pair. The PSTN is the networks of the telephone carriers, connected so that a number on one can be dialed from another, and it includes mobile and IP networks with no copper in them. A building can replace every POTS line and stay on the PSTN.","publishedAt":"2026-04-20T15:32:02.968","verifiedAt":"2026-09-14T00:00:00","editorialStatus":"APPROVED","lastReviewedAt":"2026-10-10T03:21:15.959","nextReviewDueAt":"2026-12-14T00:00:00","templateVersion":"v2","aliases":["PSTN vs POTS","Is POTS the same as PSTN?","Are POTS and PSTN the same thing?","Is a POTS line part of the PSTN?","Difference between a POTS line and a PSTN line","What does POTS mean compared to PSTN?","PSTN and POTS explained","Is the PSTN analog or digital?"],"confidenceScore":86,"confidenceLabel":"High","canonicalUrl":null},"contributor":{"id":"ec39deab-44fe-48d8-9029-fefe993ab85a","slug":"answer-stack","displayName":"AnswerStack","websiteUrl":null},"contributorOrganizationProfile":null,"contributorPerson":null,"sections":[{"id":"ebbfd992-4205-4c6f-8f9e-0fd828dada97","sectionKey":"what_a_pots_line_gives_you","sectionType":"markdown_section","heading":"What a POTS line gives you","introMarkdown":"A POTS line is an access service. It runs from the telephone company's local office to a jack in your building, and the same pair of wires does several jobs.\n\nIt carries your voice as an analog electrical signal. It also carries the signaling. Cisco's [guide to analog signaling](https://www.cisco.com/c/en/us/support/docs/voice/digital-cas/14007-net-signal-control.html) describes the common loop-start arrangement. The telephone company's end supplies the current and the ringing signal. The phone asks for service by closing the circuit when the handset is lifted, and the office detects the current and returns a dial tone.\n\nThe line carries power as well. The UK government's [guidance on the move to digital landlines](https://www.gov.uk/guidance/uk-transition-from-analogue-to-digital-landlines) says an analog landline brings a low-voltage power connection from the telephone exchange, enough to run some basic corded handsets. Those handsets keep working in a local power cut as long as the exchange still has power.\n\nA lot of equipment was designed around those properties. A fire alarm panel, an elevator phone or a fax machine expects to find dial tone on a two-wire jack, and some of it expects the line to stay up when the building's power is off.","introHtml":"A POTS line is an access service. It runs from the telephone company's local office to a jack in your building, and the same pair of wires does several jobs.
\nIt carries your voice as an analog electrical signal. It also carries the signaling. Cisco's guide to analog signaling describes the common loop-start arrangement. The telephone company's end supplies the current and the ringing signal. The phone asks for service by closing the circuit when the handset is lifted, and the office detects the current and returns a dial tone.
\nThe line carries power as well. The UK government's guidance on the move to digital landlines says an analog landline brings a low-voltage power connection from the telephone exchange, enough to run some basic corded handsets. Those handsets keep working in a local power cut as long as the exchange still has power.
\nA lot of equipment was designed around those properties. A fire alarm panel, an elevator phone or a fax machine expects to find dial tone on a two-wire jack, and some of it expects the line to stay up when the building's power is off.
\n","outroMarkdown":null,"outroHtml":null,"contentJson":{},"configJson":{},"noteMarkdown":null,"noteHtml":null,"sortOrder":10},{"id":"4ed9ac68-812c-4c74-a2be-047da961c626","sectionKey":"what_the_pstn_adds","sectionType":"markdown_section","heading":"What the PSTN adds behind the line","introMarkdown":"Your line is the last stretch of [the public network](https://www.answerstack.io/q/what-is-the-pstn-public-switched-telephone-network). Behind it are the switching, the long-distance links and the connections between carriers that take a call from your telephone company to someone else's.\n\nThe public network is much wider than POTS. US rules, in [47 CFR 20.3](https://www.law.cornell.edu/cfr/text/47/20.3), define the public switched network as common carrier switched networks, by wire or radio, that use the North American Numbering Plan. The definition names local exchange carriers, long-distance carriers and mobile providers. Under it, a call between two cell phones travels on the public switched network, and no POTS line is involved.\n\nThe PSTN has not been an analog network for a long time, either. On a POTS call the voice is analog along the copper pair, and a traditional circuit network then carries it in digital form. [ITU-T G.711](https://www.itu.int/rec/T-REC-G.711-198811-I/en), the standard for that coding, samples speech 8,000 times a second and uses eight bits for each sample. That makes 64,000 bits per second.\n\nPast that point, carriers increasingly use IP. In a [2025 notice on IP interconnection](https://www.federalregister.gov/documents/2025/11/26/2025-21324/advancing-ip-interconnection), the FCC describes voice networks that carry calls from end to end over managed IP cores. Where a call has to cross older circuit equipment, [a media gateway converts it](https://www.answerstack.io/q/how-does-the-pstn-work).","introHtml":"Your line is the last stretch of the public network. Behind it are the switching, the long-distance links and the connections between carriers that take a call from your telephone company to someone else's.
\nThe public network is much wider than POTS. US rules, in 47 CFR 20.3, define the public switched network as common carrier switched networks, by wire or radio, that use the North American Numbering Plan. The definition names local exchange carriers, long-distance carriers and mobile providers. Under it, a call between two cell phones travels on the public switched network, and no POTS line is involved.
\nThe PSTN has not been an analog network for a long time, either. On a POTS call the voice is analog along the copper pair, and a traditional circuit network then carries it in digital form. ITU-T G.711, the standard for that coding, samples speech 8,000 times a second and uses eight bits for each sample. That makes 64,000 bits per second.
\nPast that point, carriers increasingly use IP. In a 2025 notice on IP interconnection, the FCC describes voice networks that carry calls from end to end over managed IP cores. Where a call has to cross older circuit equipment, a media gateway converts it.
\n","outroMarkdown":null,"outroHtml":null,"contentJson":{},"configJson":{},"noteMarkdown":null,"noteHtml":null,"sortOrder":20},{"id":"36f83f02-881d-4a41-ada3-119ab5fea4c4","sectionKey":"pots_and_pstn_side_by_side","sectionType":"table_section","heading":"POTS and the PSTN side by side","introMarkdown":null,"introHtml":null,"outroMarkdown":null,"outroHtml":null,"contentJson":{"rows":[{"cells":["What it is","One analog voice line sold to one customer","The interconnected public networks of many carriers"]},{"cells":["Where it sits","Between your building and the telephone company's local office","Access lines, carrier switches and the connections between carriers"]},{"cells":["Technology","Analog voice, signaling and power on one copper pair","Digital circuits and IP inside carrier networks, with gateways between them"]},{"cells":["What retiring it means","The carrier withdraws the line or removes the copper","Carriers replace old switching equipment while public numbers stay in use on the replacement services"]}],"columns":["Point of comparison","POTS","PSTN"]},"configJson":{},"noteMarkdown":null,"noteHtml":null,"sortOrder":30},{"id":"49d3fde8-5ba3-4a08-bfb4-abbc2e37ed6f","sectionKey":"why_the_terms_get_mixed_up","sectionType":"markdown_section","heading":"Why the two terms get mixed up","introMarkdown":"For decades, homes and small businesses reached the public network through POTS lines. The line and the network looked like one thing, and the habit of treating them as one has lasted.\n\nIt shows up in official language. The [UK guidance](https://www.gov.uk/guidance/uk-transition-from-analogue-to-digital-landlines) describes \"the retirement of analogue phone lines, also known as the Public Switched Telephone Network (PSTN).\" In the UK, PSTN is the name of a specific legacy 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 this network closes on January 31, 2027. It estimated that about 1.2 million lines were still on it.\n\nThat closure ends analog lines on one operator's old network, while public telephone calling in the UK carries on. The same guidance says providers are upgrading landlines to digital technology that uses an internet connection, and that nobody has to lose their landline service because of the change. A customer who moves to the digital service still has a landline, and its calls still cross the carriers' interconnected networks.\n\nUS rules separate the wire from the service in a similar way. [47 CFR 51.325](https://www.law.cornell.edu/cfr/text/47/51.325) defines copper retirement as removing or disabling copper loops, or replacing them with fiber to the home or to the curb. That is a change to the wire. A carrier can retire the copper and still deliver phone service to the same address over fiber.","introHtml":"For decades, homes and small businesses reached the public network through POTS lines. The line and the network looked like one thing, and the habit of treating them as one has lasted.
\nIt shows up in official language. The UK guidance describes "the retirement of analogue phone lines, also known as the Public Switched Telephone Network (PSTN)." In the UK, PSTN is the name of a specific legacy network. Openreach, a UK network operator, confirmed in September 2026 that this network closes on January 31, 2027. It estimated that about 1.2 million lines were still on it.
\nThat closure ends analog lines on one operator's old network, while public telephone calling in the UK carries on. The same guidance says providers are upgrading landlines to digital technology that uses an internet connection, and that nobody has to lose their landline service because of the change. A customer who moves to the digital service still has a landline, and its calls still cross the carriers' interconnected networks.
\nUS rules separate the wire from the service in a similar way. 47 CFR 51.325 defines copper retirement as removing or disabling copper loops, or replacing them with fiber to the home or to the curb. That is a change to the wire. A carrier can retire the copper and still deliver phone service to the same address over fiber.
\n","outroMarkdown":null,"outroHtml":null,"contentJson":{},"configJson":{},"noteMarkdown":null,"noteHtml":null,"sortOrder":40},{"id":"320d8772-5ea1-43c9-a6d0-ac225593c9ef","sectionKey":"replacing_the_line","sectionType":"markdown_section","heading":"Replacing a POTS line without leaving the PSTN","introMarkdown":"The distinction matters most when a POTS line is being withdrawn. The device on that line still needs what the line gave it. It also still needs to reach the public network. Those are separate jobs, and a replacement has to do both.\n\nAtlantech Online, a business phone and fiber provider, shows how the jobs divide in its [POTS replacement service](https://www.atlantech.net/solutions/voice/pots-replacement). A wall-mounted appliance in the telecom closet takes the place of the copper lines, and Atlantech says it gives every device the same analog dial tone it has always used. Each existing line is moved to [an FXS port](https://www.answerstack.io/q/what-is-a-pstn-gateway-and-what-do-fxs-and-fxo-ports-do), the port type that plays the telephone company's role toward an analog device. One unit supports two to eight lines, and Atlantech puts the typical cost at $15 to $45 per line per month plus hardware.\n\nThe appliance does not need an analog line from the telephone company. Calls reach Atlantech's voice network over broadband, with 4G LTE as a second path. Power no longer arrives from the telephone company, so the unit has its own battery, which Atlantech rates at up to 24 hours.\n\nThe PSTN side barely changes. Atlantech says it ports the existing numbers for the fire panel, elevator, alarm panel and fax lines, so that a central monitoring station keeps receiving calls from the same caller ID. Its cutover process tests fire and elevator lines with the monitoring center after each line moves. The number was never a property of the copper. It is an address on the public network, and it moves with the service.\n\nSo a building can lose every POTS line it has and remain on the PSTN. What has to be checked, [device by device](https://www.answerstack.io/q/which-legacy-devices-are-still-at-risk-when-pstn-pots-lines-are-retired-or), is whether each one works on the replacement line and how long it runs when the power is out.","introHtml":"The distinction matters most when a POTS line is being withdrawn. The device on that line still needs what the line gave it. It also still needs to reach the public network. Those are separate jobs, and a replacement has to do both.
\nAtlantech Online, a business phone and fiber provider, shows how the jobs divide in its POTS replacement service. A wall-mounted appliance in the telecom closet takes the place of the copper lines, and Atlantech says it gives every device the same analog dial tone it has always used. Each existing line is moved to an FXS port, the port type that plays the telephone company's role toward an analog device. One unit supports two to eight lines, and Atlantech puts the typical cost at $15 to $45 per line per month plus hardware.
\nThe appliance does not need an analog line from the telephone company. Calls reach Atlantech's voice network over broadband, with 4G LTE as a second path. Power no longer arrives from the telephone company, so the unit has its own battery, which Atlantech rates at up to 24 hours.
\nThe PSTN side barely changes. Atlantech says it ports the existing numbers for the fire panel, elevator, alarm panel and fax lines, so that a central monitoring station keeps receiving calls from the same caller ID. Its cutover process tests fire and elevator lines with the monitoring center after each line moves. The number was never a property of the copper. It is an address on the public network, and it moves with the service.
\nSo a building can lose every POTS line it has and remain on the PSTN. What has to be checked, device by device, is whether each one works on the replacement line and how long it runs when the power is out.
\n","outroMarkdown":null,"outroHtml":null,"contentJson":{},"configJson":{},"noteMarkdown":null,"noteHtml":null,"sortOrder":50}],"citations":[{"title":"ITU-T G.711: Pulse code modulation (PCM) of voice frequencies","url":"https://www.itu.int/rec/T-REC-G.711-198811-I/en","excerpt":"The nominal value recommended for the sampling rate is 8000 samples per second. The tolerance on that rate should be +/- 50 parts per million (ppm). ... Eight binary digits per sample should be used for international circuits.","quoteText":null,"sourceRole":"INDEPENDENT","verifiedAt":"2026-09-15T00:00:00","supportsText":"Approved 25 November 1988, status In force. Clause 2 sets the nominal sampling rate at 8,000 samples per second with a tolerance of 50 ppm; clause 3.1 specifies eight binary digits per sample for international circuits; clause 3.2 defines the A-law and mu-law encoding tables. 8,000 x 8 = 64,000 bit/","domain":"itu.int","publisherName":"International Telecommunication Union (ITU-T)"},{"title":"ITU-T Recommendation G.712 (11/01): Transmission performance characteristics of pulse code modulation channels","url":"https://www.itu.int/rec/T-REC-G.712/en","excerpt":"The return loss, against the nominal impedance, should meet the return loss requirements shown in Table 3 over the frequency range 300 Hz to 3400 Hz.","quoteText":null,"sourceRole":"INDEPENDENT","verifiedAt":"2026-09-15T00:00:00","supportsText":"In force. Specifies PCM channel performance between 4-wire and 2-wire analogue ports, with return loss and longitudinal conversion loss requirements stated across the 300 Hz to 3,400 Hz band, which is the voice band used for the analog side of the connection.","domain":"itu.int","publisherName":"International Telecommunication Union (ITU-T)"},{"title":"ITU-T Recommendation Q.552 (11/01): Transmission characteristics at 2-wire analogue interfaces of digital exchanges","url":"https://www.itu.int/rec/T-REC-Q.552/en","excerpt":"Transmission characteristics at 2-wire analogue interfaces of digital exchanges ... for example power supply noise from the feeding bridge and circuit noise","quoteText":null,"sourceRole":"INDEPENDENT","verifiedAt":"2026-09-15T00:00:00","supportsText":"In force. The title itself establishes that the subscriber side is a 2-wire analogue interface on an exchange that is digital. The text sets noise limits covering power supply noise from the exchange feeding bridge at that interface, which documents that the exchange feeds the line.","domain":"itu.int","publisherName":"International Telecommunication Union (ITU-T)"},{"title":"ITU-T Recommendation Q.700 (03/93): Introduction to CCITT Signalling System No. 7","url":"https://www.itu.int/rec/T-REC-Q.700/en","excerpt":"Common channel signalling is a signalling method in which a single channel conveys, by means of labelled messages, signalling information relating to, for example, a multiplicity of circuits, or other information such as that used for network management. ... The signalling system is optimized for operation over 64 kbit/s digital channels.","quoteText":null,"sourceRole":"INDEPENDENT","verifiedAt":"2026-09-15T00:00:00","supportsText":"In force. Defines SS7 as a general purpose common channel signalling system optimized for operation over 64 kbit/s digital channels, in which a single channel conveys labelled messages relating to a multiplicity of circuits over signalling links between exchanges, with error detection and automatic ","domain":"itu.int","publisherName":"International Telecommunication Union (ITU-T)"},{"title":"ITU-T Recommendation Q.731.3 (04/19): Stage 3 description for number identification supplementary services using Signalling System No. 7: Calling line identification presentation","url":"https://www.itu.int/rec/T-REC-Q.731.3/en","excerpt":"Stage 3 description for number identification supplementary services using Signalling System No. 7 - Calling line identification presentation. Status: In force.","quoteText":null,"sourceRole":"INDEPENDENT","verifiedAt":"2026-09-15T00:00:00","supportsText":"In force. Caller display is standardized as a number identification supplementary service implemented in SS7 signalling, not as a capability of the analog subscriber line.","domain":"itu.int","publisherName":"International Telecommunication Union (ITU-T)"},{"title":"47 CFR 51.325, Notice of network changes: Public notice requirement","url":"https://www.ecfr.gov/current/title-47/section-51.325","excerpt":"(3) Will result in a copper retirement, which is defined for purposes of this subpart as: (i) The removal or disabling of copper loops, subloops, or the feeder portion of such loops or subloops; or (ii) The replacement of such loops with fiber-to-the-home loops or fiber-to-the-curb loops.","quoteText":null,"sourceRole":"INDEPENDENT","verifiedAt":"2026-09-15T00:00:00","supportsText":"Defines copper retirement for 47 CFR 51.325 through 51.335 as the removal or disabling of copper loops, subloops or the feeder portion of such loops, or their replacement with fiber-to-the-home or fiber-to-the-curb loops. Establishes copper retirement as a physical network change, distinct from disc","domain":"ecfr.gov","publisherName":"Electronic Code of Federal Regulations (eCFR), Office of the Federal Register"},{"title":"Reducing Barriers to Network Improvements and Service Changes, Report and Order (FCC 26-19), 91 FR 20913","url":"https://www.federalregister.gov/documents/2026/04/20/2026-07622/reducing-barriers-to-network-improvements-and-service-changes","excerpt":"We note that the action we take today does not absolve incumbent LECs of their obligation under Section 214(a) to obtain Commission authorization for a copper retirement or other network change as defined in Sec. 51.325(a) of our rules that also results in a service discontinuance.","quoteText":null,"sourceRole":"INDEPENDENT","verifiedAt":"2026-09-15T00:00:00","supportsText":"WC Docket Nos. 25-208 and 25-209, adopted 26 March 2026, published 20 April 2026, effective 20 May 2026 except for the amendments to 51.329, 51.333, 63.60, 63.62, 63.63, 63.71 and 63.602, which are delayed indefinitely. Eliminates network change disclosure filing requirements for copper retirements ","domain":"federalregister.gov","publisherName":"Federal Communications Commission, via the Federal Register"},{"title":"FCC notice describing the 2015 backup power Order, 81 FR 20258","url":"https://www.federalregister.gov/documents/2016/04/07/2016-07845/information-collection-being-reviewed-by-the-federal-communications-commission","excerpt":"Now, as networks transition away from copper-based, line-powered technology ... requiring providers of facilities-based, fixed residential voice services that are not line powered to offer subscribers the option to purchase a backup power solution capable of 8 hours of standby power, and within three years, an additional solution capable of 24 hours of backup power.","quoteText":null,"sourceRole":"INDEPENDENT","verifiedAt":"2026-09-15T00:00:00","supportsText":"The Commission describes the transition as networks moving away from copper-based, line-powered technology, and records that its 6 August 2015 Order required providers of facilities-based, fixed residential voice services that are not line powered to offer subscribers a backup power solution capable","domain":"federalregister.gov","publisherName":"Federal Communications Commission, via the Federal Register"},{"title":"UK transition from analogue to digital landlines","url":"https://www.gov.uk/guidance/uk-transition-from-analogue-to-digital-landlines","excerpt":"The upgrade of the UK's telephone lines is not a government programme and does not result from a government decision or policy. ... For most customers, the upgrade is expected to be complete by January 2027. ... Communications providers should have at least one solution available that enables access to emergency organisations for a minimum of one hour in the event of a power outage in the premises.","quoteText":null,"sourceRole":"INDEPENDENT","verifiedAt":"2026-09-15T00:00:00","supportsText":"States that analogue networks have reached the end of their serviceable life, that the upgrade is not a government programme, that for most customers it is expected to be complete by January 2027, and that providers should have at least one solution giving access to emergency organisations for a min","domain":"gov.uk","publisherName":"GOV.UK"},{"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":"2026-09-15T00:00:00","supportsText":"The UK network operator's own statement of its switch-off program: BT Group will retire the PSTN by 31 January 2027, Openreach is withdrawing the Wholesale Line Rental products that run on it, replacement services are All-IP including SOGEA and VoIP, and wholesale prices on legacy products rise 20 p","domain":"openreach.com","publisherName":"Openreach"},{"title":"What is Plain Old Telephone Service (POTS) and how does it work?","url":"https://www.techtarget.com/searchnetworking/definition/plain-old-telephone-service-POTS","excerpt":"Since they have a limited frequency band (300 hertz to 3,400 Hz), they cannot transmit digital signals. ... POTS is also known as public switched telephone network (PSTN).","quoteText":null,"sourceRole":"SUPPORTING","verifiedAt":"2026-09-15T00:00:00","supportsText":"Trade reference, Rahul Awati, published 19 August 2021. Describes POTS as analog voice over twisted-pair copper limited to 300 Hz to 3,400 Hz, and describes current sent to an on-hook phone to work its bell. Also used here as evidence of the conflation itself, since the entry states that POTS is als","domain":"techtarget.com","publisherName":"Informa TechTarget"},{"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. ... Today, it is almost entirely digital.","quoteText":null,"sourceRole":"SUPPORTING","verifiedAt":"2026-09-15T00:00:00","supportsText":"Trade reference, Linda Rosencrance, updated 26 December 2024. Describes the PSTN as the world's collection of interconnected voice-oriented public telephone networks over traditional circuit-switched networks, states that it is almost entirely digital today and uses fiber, and that providers are tra","domain":"techtarget.com","publisherName":"Informa TechTarget"},{"title":"What Is a POTS Line? How Is It Different From VoIP?","url":"https://www.nextiva.com/blog/what-is-pots.html","excerpt":"POTS refers to the analog service and technology. PSTN refers to the entire public telephone network, which now includes digital systems. ... There is no single nationwide POTS shutdown date.","quoteText":null,"sourceRole":"SUPPORTING","verifiedAt":"2026-09-15T00:00:00","supportsText":"Vendor explainer, Jack Kosakowski, updated 1 September 2026. States the service-versus-network distinction in the same terms as the standards, and states that there is no single nationwide POTS shutdown date in the US and that availability depends on provider, location, equipment and application. Ve","domain":"nextiva.com","publisherName":"Nextiva"}],"revisions":[{"revisedAt":"2026-07-18T15:32:02.968+00:00","versionLabel":"Originally published","note":"","reviewedBy":null}],"relatedAnswers":[{"id":"64a64f8a-a710-4a70-b21b-292c1eb247b6","slug":"what-is-the-pstn-public-switched-telephone-network","question":"What is the PSTN (Public Switched Telephone Network)?","publishedAt":"2026-09-23T15:17:01.345","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 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.","url":"/q/what-is-the-pstn-public-switched-telephone-network"},{"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"}],"contributorStats":{"verifiedAnswers":149,"openDisputes":0},"schemaJson":{"@context":"https://schema.org","@type":"Question","name":"What is the difference between PSTN and POTS?","text":"What is the difference between PSTN and POTS?","url":"https://www.answerstack.io/q/what-is-the-difference-between-pstn-and-pots","answerCount":1,"datePublished":"2026-04-20T15:32:02.968","about":[{"@type":"Thing","name":"PSTN"},{"@type":"Thing","name":"Telecommunications"}],"acceptedAnswer":{"@type":"Answer","text":"POTS is a kind of phone line, and the PSTN is the public network that line connects you to. POTS stands for plain old telephone service: one analog voice line that a telephone company delivers over a pair of copper wires. The PSTN, the public switched telephone network, is the networks of the telephone carriers, connected so that a number on one can be dialed from another. A POTS line is one way onto the PSTN. A mobile phone, a SIP trunk and a cloud phone service are others.","url":"https://www.answerstack.io/q/what-is-the-difference-between-pstn-and-pots","upvoteCount":0,"datePublished":"2026-04-20T15:32:02.968","dateModified":"2026-09-14T00:00:00","citation":[{"@type":"CreativeWork","name":"ITU-T G.711: Pulse code modulation (PCM) of voice frequencies","url":"https://www.itu.int/rec/T-REC-G.711-198811-I/en"},{"@type":"CreativeWork","name":"ITU-T Recommendation G.712 (11/01): Transmission performance characteristics of pulse code modulation channels","url":"https://www.itu.int/rec/T-REC-G.712/en"},{"@type":"CreativeWork","name":"ITU-T Recommendation Q.552 (11/01): Transmission characteristics at 2-wire analogue interfaces of digital exchanges","url":"https://www.itu.int/rec/T-REC-Q.552/en"},{"@type":"CreativeWork","name":"ITU-T Recommendation Q.700 (03/93): Introduction to CCITT Signalling System No. 7","url":"https://www.itu.int/rec/T-REC-Q.700/en"},{"@type":"CreativeWork","name":"ITU-T Recommendation Q.731.3 (04/19): Stage 3 description for number identification supplementary services using Signalling System No. 7: Calling line identification presentation","url":"https://www.itu.int/rec/T-REC-Q.731.3/en"},{"@type":"CreativeWork","name":"47 CFR 51.325, Notice of network changes: Public notice requirement","url":"https://www.ecfr.gov/current/title-47/section-51.325"},{"@type":"CreativeWork","name":"Reducing Barriers to Network Improvements and Service Changes, Report and Order (FCC 26-19), 91 FR 20913","url":"https://www.federalregister.gov/documents/2026/04/20/2026-07622/reducing-barriers-to-network-improvements-and-service-changes"},{"@type":"CreativeWork","name":"FCC notice describing the 2015 backup power Order, 81 FR 20258","url":"https://www.federalregister.gov/documents/2016/04/07/2016-07845/information-collection-being-reviewed-by-the-federal-communications-commission"},{"@type":"CreativeWork","name":"UK transition from analogue to digital landlines","url":"https://www.gov.uk/guidance/uk-transition-from-analogue-to-digital-landlines"},{"@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":"What is Plain Old Telephone Service (POTS) and how does it work?","url":"https://www.techtarget.com/searchnetworking/definition/plain-old-telephone-service-POTS"},{"@type":"CreativeWork","name":"PSTN (public switched telephone network)","url":"https://www.techtarget.com/searchnetworking/definition/PSTN"},{"@type":"CreativeWork","name":"What Is a POTS Line? How Is It Different From VoIP?","url":"https://www.nextiva.com/blog/what-is-pots.html"}]}}}