The difference is one of scope: the public switched telephone network, or PSTN, is the entire interconnected system of operator-run telephone networks, while plain old telephone service, or POTS, is the basic analog voice service delivered to a subscriber over that system.[1][2] POTS is therefore a service that runs on the PSTN, not a separate network, which is why the two names often get used for the same thing.[2][4] Technically, POTS is analog from end to end over a copper pair and limited to a narrow voice band of roughly 300 to 3,400 hertz, whereas the PSTN's core has been digital for decades, encoding each call as a 64 kbit/s stream.[1][3][6] Both are now being retired together as carriers move voice onto internet protocol networks, and the United Kingdom is scheduled to switch off its PSTN, and the POTS lines it carries, by 31 January 2027.[7][8]
\n","summary":"POTS and the PSTN describe two layers of the same telephone system. Plain old telephone service is the basic analog voice product on a single copper line, while the PSTN is the whole switched network of exchanges and trunks that carries the call. POTS runs on the PSTN rather than beside it, which is why the two terms get used interchangeably. The core of the PSTN is digital, while POTS stays analog at the edge, and both are now being retired as voice moves to internet protocol.","publishedAt":"2026-07-18T15:32:02.968","verifiedAt":"2026-07-18T00:00:00","editorialStatus":"APPROVED","lastReviewedAt":"2026-07-18T00:00:00","nextReviewDueAt":"2026-10-18T00:00:00","templateVersion":"v2","aliases":["PSTN vs POTS","What is the difference between POTS and PSTN?","Is POTS the same as PSTN?","POTS vs PSTN explained","Difference between plain old telephone service and the public switched telephone network","Are PSTN and POTS the same thing?","POTS meaning vs PSTN meaning","How is POTS different from the PSTN?","PSTN and POTS comparison","Is a POTS line part of the PSTN?","What is POTS and what is PSTN?","PSTN versus POTS lines"],"confidenceScore":92,"confidenceLabel":"High","canonicalUrl":null},"contributor":{"id":"ec39deab-44fe-48d8-9029-fefe993ab85a","slug":"answer-stack","displayName":"AnswerStack","websiteUrl":null},"contributorOrganizationProfile":{"entityId":"ec39deab-44fe-48d8-9029-fefe993ab85a","legalName":null,"description":null,"websiteUrl":null,"imageUrl":null,"slogan":null,"subtitle":null,"facts":[],"coiNote":null,"foundingDate":null,"numberOfEmployeesText":null,"contactPoint":null,"address":null,"headquartersText":null,"organizationType":null},"contributorPerson":{"slug":"answerstack-editorial-team","displayName":"AnswerStack Editorial Team"},"sections":[{"id":"56625385-5500-4ff2-a68a-a9b2f3587f52","sectionKey":"pstn_pots_relationship","sectionType":"markdown_section","heading":"How do PSTN and POTS relate?","introMarkdown":"PSTN and POTS describe two different layers of the same telephone system: one is the network, the other is a service that runs on it. The public switched telephone network is the aggregate of the world's interconnected, operator-run telephone networks, the physical and logical system of exchanges and trunks, plus the switches that route a call between any two phones.[1] Plain old telephone service is the basic, two-way analog voice service that reaches a subscriber over a copper line, the ordinary landline most people grew up with.[2] Every POTS line depends on the PSTN to complete a call, but the PSTN carries much more than plain voice, so POTS is best understood as one service the network delivers rather than a rival to it.[1][2]\n\n### Why the two names blur together\n\nFor a home phone user, POTS and the PSTN arrive as the same thing. When you picked up an analog handset and heard a dial tone, you were using POTS, and the call it placed traveled across the PSTN.[2][4] Reference sources carry that overlap: some define POTS as the analog way of accessing the PSTN, and at least one industry glossary lists the PSTN as also being known as plain old telephone service.[1][4] The distinction still matters, because the PSTN also carries digital services, business trunks, and the signaling that plain telephone service never touched, and because the two are being retired on the same timeline as voice moves to internet protocol.[1][7]\n\nPut simply, POTS is the service a customer buys on a single line, and the PSTN is the switched system that connects that line to every other phone. Keeping the two straight matters most during a migration, because retiring the analog service on a line is not the same event as rebuilding the network beneath it, even if the current transition happens to do both.[1][7]","introHtml":"PSTN and POTS describe two different layers of the same telephone system: one is the network, the other is a service that runs on it. The public switched telephone network is the aggregate of the world's interconnected, operator-run telephone networks, the physical and logical system of exchanges and trunks, plus the switches that route a call between any two phones.[1] Plain old telephone service is the basic, two-way analog voice service that reaches a subscriber over a copper line, the ordinary landline most people grew up with.[2] Every POTS line depends on the PSTN to complete a call, but the PSTN carries much more than plain voice, so POTS is best understood as one service the network delivers rather than a rival to it.[1][2]
\nFor a home phone user, POTS and the PSTN arrive as the same thing. When you picked up an analog handset and heard a dial tone, you were using POTS, and the call it placed traveled across the PSTN.[2][4] Reference sources carry that overlap: some define POTS as the analog way of accessing the PSTN, and at least one industry glossary lists the PSTN as also being known as plain old telephone service.[1][4] The distinction still matters, because the PSTN also carries digital services, business trunks, and the signaling that plain telephone service never touched, and because the two are being retired on the same timeline as voice moves to internet protocol.[1][7]
\nPut simply, POTS is the service a customer buys on a single line, and the PSTN is the switched system that connects that line to every other phone. Keeping the two straight matters most during a migration, because retiring the analog service on a line is not the same event as rebuilding the network beneath it, even if the current transition happens to do both.[1][7]
\n","outroMarkdown":null,"outroHtml":null,"contentJson":{},"configJson":{},"noteMarkdown":null,"noteHtml":null,"sortOrder":0},{"id":"c60285f2-bad4-4dbb-b990-eb9df2a3317e","sectionKey":"comparison_table","sectionType":"table_section","heading":"PSTN and POTS at a glance","introMarkdown":"The two differ mainly in scope and in the kind of signal each one uses. The table sets them side by side, and the sections after it explain each row and why the difference matters.","introHtml":"The two differ mainly in scope and in the kind of signal each one uses. The table sets them side by side, and the sections after it explain each row and why the difference matters.
\n","outroMarkdown":"The rows overlap because POTS sits inside the PSTN. Each one is described in full below.","outroHtml":"The rows overlap because POTS sits inside the PSTN. Each one is described in full below.
\n","contentJson":{"rows":[{"cells":["What it is","The whole switched telephone network [1]","A basic analog voice service on that network [2]"]},{"cells":["Scope","A system of exchanges, trunks, and switches [1]","One service on a single subscriber line [2]"]},{"cells":["Signal","Digital in the core, analog only at the edge [1]","Analog from end to end over a copper pair [3]"]},{"cells":["What 'switched' means","Circuit switching across a hierarchy of exchanges [4]","A plain voice path that relies on that switching [2]"]},{"cells":["Typical use","Voice, business trunks, signaling, legacy data [4]","Two-way voice, powered from the exchange [2]"]},{"cells":["Being retired?","Yes, moving to IP; UK switch-off by 31 Jan 2027 [7]","Yes, the copper lines are withdrawn with it [5]"]}],"columns":["Dimension","PSTN","POTS"]},"configJson":{},"noteMarkdown":null,"noteHtml":null,"sortOrder":1},{"id":"d47203c1-93c8-4d0d-9c15-3b6aaf2c5826","sectionKey":"network_vs_service","sectionType":"markdown_section","heading":"PSTN is the network; POTS is the service it delivers","introMarkdown":"The clearest way to separate the two is by scope: the PSTN is infrastructure, and POTS is a service that infrastructure provides. The public switched telephone network is the system of local loops, exchanges, trunks, and switches that any call travels through, owned not by one company but by many carriers interconnecting under shared standards.[1] Plain old telephone service is what a subscriber actually receives on their line: a dial tone and a two-way voice path that reaches any other number.[2] You can run the network without a given service on it, but you cannot have the service without the network, which is why POTS sits inside the PSTN rather than beside it.[1][2] For a business deciding what to replace, the practical takeaway is that dropping POTS lines changes the service on your premises, while the PSTN switch-off changes the carrier network those lines depend on.[5][7]","introHtml":"The clearest way to separate the two is by scope: the PSTN is infrastructure, and POTS is a service that infrastructure provides. The public switched telephone network is the system of local loops, exchanges, trunks, and switches that any call travels through, owned not by one company but by many carriers interconnecting under shared standards.[1] Plain old telephone service is what a subscriber actually receives on their line: a dial tone and a two-way voice path that reaches any other number.[2] You can run the network without a given service on it, but you cannot have the service without the network, which is why POTS sits inside the PSTN rather than beside it.[1][2] For a business deciding what to replace, the practical takeaway is that dropping POTS lines changes the service on your premises, while the PSTN switch-off changes the carrier network those lines depend on.[5][7]
\n","outroMarkdown":null,"outroHtml":null,"contentJson":{},"configJson":{},"noteMarkdown":null,"noteHtml":null,"sortOrder":2},{"id":"37f320c5-6b5d-4931-8585-f1bec2a061e0","sectionKey":"analog_vs_digital","sectionType":"markdown_section","heading":"POTS is analog; the PSTN core is digital","introMarkdown":"POTS is analog from the handset to the exchange, while the core of the PSTN has been digital for decades, and that split is the source of much of the confusion. A plain telephone line carries the voice as a continuously varying electrical signal over a copper pair, confined to a narrow band of roughly 300 to 3,400 hertz, which is enough for intelligible speech but well short of full-range audio.[3] Once that analog signal reaches the local exchange, the PSTN converts it into digital form, sampling the voice 8,000 times a second and coding each sample to produce a single 64 kbit/s channel defined by the ITU-T G.711 standard.[6][1] From there the call crosses the network as digital data and is turned back into analog only for the copper line at the far end.[1] So a normal landline call is analog at both edges and digital in the middle, and POTS names the analog edge while the PSTN names the whole path, most of which is no longer analog at all.[1][3]","introHtml":"POTS is analog from the handset to the exchange, while the core of the PSTN has been digital for decades, and that split is the source of much of the confusion. A plain telephone line carries the voice as a continuously varying electrical signal over a copper pair, confined to a narrow band of roughly 300 to 3,400 hertz, which is enough for intelligible speech but well short of full-range audio.[3] Once that analog signal reaches the local exchange, the PSTN converts it into digital form, sampling the voice 8,000 times a second and coding each sample to produce a single 64 kbit/s channel defined by the ITU-T G.711 standard.[6][1] From there the call crosses the network as digital data and is turned back into analog only for the copper line at the far end.[1] So a normal landline call is analog at both edges and digital in the middle, and POTS names the analog edge while the PSTN names the whole path, most of which is no longer analog at all.[1][3]
\n","outroMarkdown":null,"outroHtml":null,"contentJson":{},"configJson":{},"noteMarkdown":null,"noteHtml":null,"sortOrder":3},{"id":"092fb259-afd7-4b8c-a34a-5c02c7d8a010","sectionKey":"switching_and_features","sectionType":"markdown_section","heading":"What 'switched' means, and why POTS is the plain case","introMarkdown":"The word switched in PSTN refers to circuit switching, the method the network uses to build a temporary dedicated path for each call, and POTS is the most basic use of that capability. When a POTS line places a call, the PSTN's switches read the dialed number and connect a path through a hierarchy of exchanges, holding that circuit open for the length of the conversation.[4] Plain telephone service adds nothing to this arrangement: it is a point-to-point voice line that depends on the network's switching to reach the other end, without a data channel or signaling features of its own.[2] The routing and the call setup live in the PSTN, not in the POTS line.[1][4]\n\n### POTS is bare voice; the PSTN carries more\n\nBeyond that single voice path, POTS provides very little, while the PSTN also carries the signaling and numbering, plus the business services that plain telephone service never included. A POTS line is powered from the exchange, typically at about 48 volts of direct current backed by central-office batteries, which is why a wired analog phone usually kept working during a household power cut.[2] Features such as caller identification depend on the wider network rather than the line itself.[2] The PSTN also supports business trunks and the signaling that sets up calls, along with legacy digital services such as ISDN that emerged on the same infrastructure.[4][1] For a buyer, this is why a modern replacement has to account for more than dial tone: an old POTS line may quietly be running a life-safety circuit such as a fire panel or elevator phone that assumed the line would stay powered and available.[9][5]","introHtml":"The word switched in PSTN refers to circuit switching, the method the network uses to build a temporary dedicated path for each call, and POTS is the most basic use of that capability. When a POTS line places a call, the PSTN's switches read the dialed number and connect a path through a hierarchy of exchanges, holding that circuit open for the length of the conversation.[4] Plain telephone service adds nothing to this arrangement: it is a point-to-point voice line that depends on the network's switching to reach the other end, without a data channel or signaling features of its own.[2] The routing and the call setup live in the PSTN, not in the POTS line.[1][4]
\nBeyond that single voice path, POTS provides very little, while the PSTN also carries the signaling and numbering, plus the business services that plain telephone service never included. A POTS line is powered from the exchange, typically at about 48 volts of direct current backed by central-office batteries, which is why a wired analog phone usually kept working during a household power cut.[2] Features such as caller identification depend on the wider network rather than the line itself.[2] The PSTN also supports business trunks and the signaling that sets up calls, along with legacy digital services such as ISDN that emerged on the same infrastructure.[4][1] For a buyer, this is why a modern replacement has to account for more than dial tone: an old POTS line may quietly be running a life-safety circuit such as a fire panel or elevator phone that assumed the line would stay powered and available.[9][5]
\n","outroMarkdown":null,"outroHtml":null,"contentJson":{},"configJson":{},"noteMarkdown":null,"noteHtml":null,"sortOrder":4},{"id":"6f81c144-0599-4ac6-8bbc-4069157f15a1","sectionKey":"interchangeable_terms","sectionType":"markdown_section","heading":"Why do people use PSTN and POTS interchangeably?","introMarkdown":"People treat PSTN and POTS as synonyms because, for an ordinary landline, they describe the same experience from two different angles. To a residential caller there was never a visible boundary between the service and the network, since the analog line and the call it placed across the country felt like a single thing.[2][4] Technical writing has absorbed that habit, so you will find POTS defined as the analog way of accessing the PSTN, and you will also find the PSTN listed as being known as plain old telephone service.[1][4] The looseness is usually harmless, but it hides a real distinction: the PSTN carries services that are not POTS, including business-grade digital lines and the signaling that makes the whole system work, none of which a plain telephone line ever used.[1][4] In a migration plan the difference resurfaces, because a provider can retire the analog POTS product on your line while the underlying network keeps running, and it can also rebuild the network underneath you while your service appears unchanged.[5][7]","introHtml":"People treat PSTN and POTS as synonyms because, for an ordinary landline, they describe the same experience from two different angles. To a residential caller there was never a visible boundary between the service and the network, since the analog line and the call it placed across the country felt like a single thing.[2][4] Technical writing has absorbed that habit, so you will find POTS defined as the analog way of accessing the PSTN, and you will also find the PSTN listed as being known as plain old telephone service.[1][4] The looseness is usually harmless, but it hides a real distinction: the PSTN carries services that are not POTS, including business-grade digital lines and the signaling that makes the whole system work, none of which a plain telephone line ever used.[1][4] In a migration plan the difference resurfaces, because a provider can retire the analog POTS product on your line while the underlying network keeps running, and it can also rebuild the network underneath you while your service appears unchanged.[5][7]
\n","outroMarkdown":null,"outroHtml":null,"contentJson":{},"configJson":{},"noteMarkdown":null,"noteHtml":null,"sortOrder":5},{"id":"fa28bac2-dc1a-4b83-beae-9de45c4a8fb7","sectionKey":"retirement","sectionType":"markdown_section","heading":"What retiring POTS and the PSTN actually means","introMarkdown":"Retiring POTS and the PSTN means moving telephone calls off dedicated copper circuits and onto internet protocol networks, a change carriers are making because the old equipment is expensive to keep running.[5] The switch is happening on both sides of the Atlantic, though the timelines and the way they are framed differ.\n\n### The UK switch-off has a fixed date\n\nIn the United Kingdom the transition has a hard deadline: BT Group plans to retire the PSTN by 31 January 2027, after which landline calls run over broadband as Voice over IP.[7] Openreach, which operates the physical network most UK providers rely on, has been withdrawing the products that depend on the old network and has stopped selling new copper-based lines.[7] The UK government describes the analog network as having reached the end of its serviceable life and treats the move to digital landlines as an industry-led program expected to be substantially complete by the same date.[8] Because a digital line does not draw power from the exchange the way a POTS line did, providers must offer a way to keep reaching emergency services for at least an hour during a power cut, usually a battery backup unit.[8]\n\n### The US copper sunset runs on a looser timeline\n\nIn the United States the same shift is underway without a single national switch-off date. Carriers are transitioning the PSTN to all-IP, and most households have already moved to wireless or internet-based calling.[4][5] Regulators have cleared the path by relieving carriers of the obligation to maintain aging copper, so companies including AT&T and Verizon have been decommissioning copper networks and steering customers toward fiber and wireless.[5] One visible effect for businesses still on analog lines is price, since standalone POTS service has grown markedly more expensive as carriers add copper surcharges to encourage migration.[9][5]","introHtml":"Retiring POTS and the PSTN means moving telephone calls off dedicated copper circuits and onto internet protocol networks, a change carriers are making because the old equipment is expensive to keep running.[5] The switch is happening on both sides of the Atlantic, though the timelines and the way they are framed differ.
\nIn the United Kingdom the transition has a hard deadline: BT Group plans to retire the PSTN by 31 January 2027, after which landline calls run over broadband as Voice over IP.[7] Openreach, which operates the physical network most UK providers rely on, has been withdrawing the products that depend on the old network and has stopped selling new copper-based lines.[7] The UK government describes the analog network as having reached the end of its serviceable life and treats the move to digital landlines as an industry-led program expected to be substantially complete by the same date.[8] Because a digital line does not draw power from the exchange the way a POTS line did, providers must offer a way to keep reaching emergency services for at least an hour during a power cut, usually a battery backup unit.[8]
\nIn the United States the same shift is underway without a single national switch-off date. Carriers are transitioning the PSTN to all-IP, and most households have already moved to wireless or internet-based calling.[4][5] Regulators have cleared the path by relieving carriers of the obligation to maintain aging copper, so companies including AT&T and Verizon have been decommissioning copper networks and steering customers toward fiber and wireless.[5] One visible effect for businesses still on analog lines is price, since standalone POTS service has grown markedly more expensive as carriers add copper surcharges to encourage migration.[9][5]
\n","outroMarkdown":null,"outroHtml":null,"contentJson":{},"configJson":{},"noteMarkdown":null,"noteHtml":null,"sortOrder":6},{"id":"0ba6195d-c236-4860-9745-604471dd901e","sectionKey":"trade_offs","sectionType":"markdown_section","heading":"Trade-offs and limits worth knowing","introMarkdown":"The strengths and weaknesses of POTS and the PSTN both come from their age and their circuit-switched design. Reliability is the classic argument for POTS, because the line carries its own power from the exchange, so a basic analog phone usually kept working when the mains failed, which is exactly the property digital replacements have to recreate with backup batteries.[2][8] Voice quality and call setup are consistent too, since circuit switching reserves capacity for each call rather than sharing it the way packet networks do.[4]\n\nThe limits are just as real. A POTS line is confined to a narrow voice band, so it was never a path for anything beyond speech and slow dial-up data.[3] Holding a full circuit open for every call, including the silent gaps, uses network capacity less efficiently than internet protocol, which is part of why carriers prefer IP.[4][1] The maintenance cost is the deciding factor now, because the copper plant and the switches behind it are decades old and increasingly hard to support, so the timing of a migration is set more by the carrier's retirement schedule than by the customer's preference.[5][7]","introHtml":"The strengths and weaknesses of POTS and the PSTN both come from their age and their circuit-switched design. Reliability is the classic argument for POTS, because the line carries its own power from the exchange, so a basic analog phone usually kept working when the mains failed, which is exactly the property digital replacements have to recreate with backup batteries.[2][8] Voice quality and call setup are consistent too, since circuit switching reserves capacity for each call rather than sharing it the way packet networks do.[4]
\nThe limits are just as real. A POTS line is confined to a narrow voice band, so it was never a path for anything beyond speech and slow dial-up data.[3] Holding a full circuit open for every call, including the silent gaps, uses network capacity less efficiently than internet protocol, which is part of why carriers prefer IP.[4][1] The maintenance cost is the deciding factor now, because the copper plant and the switches behind it are decades old and increasingly hard to support, so the timing of a migration is set more by the carrier's retirement schedule than by the customer's preference.[5][7]
\n","outroMarkdown":null,"outroHtml":null,"contentJson":{},"configJson":{},"noteMarkdown":null,"noteHtml":null,"sortOrder":7},{"id":"d2487efa-fb02-483d-a6db-bf084240f10c","sectionKey":"contributor_perspective","sectionType":"markdown_section","heading":"How this answer was researched","introMarkdown":"This entry draws its definitions from reference and industry sources and its technical claims from the standard that defines digital telephone voice. The distinction between the network and the service comes from encyclopedia and glossary entries that were cross-checked against each other, and the digital-encoding detail from ITU-T G.711.[1][2][3][4][5][6] The retirement claims are taken from the network operator and the government guidance that set and describe the 31 January 2027 date, rather than from secondary summaries.[7][8] Telephone networks and their retirement schedules change, so the dates and prices here reflect what the cited sources stated on the verification date. Engineers, regulators, and carriers who work on these systems are welcome to suggest corrections, which are checked against primary sources before any update.","introHtml":"This entry draws its definitions from reference and industry sources and its technical claims from the standard that defines digital telephone voice. The distinction between the network and the service comes from encyclopedia and glossary entries that were cross-checked against each other, and the digital-encoding detail from ITU-T G.711.[1][2][3][4][5][6] The retirement claims are taken from the network operator and the government guidance that set and describe the 31 January 2027 date, rather than from secondary summaries.[7][8] Telephone networks and their retirement schedules change, so the dates and prices here reflect what the cited sources stated on the verification date. Engineers, regulators, and carriers who work on these systems are welcome to suggest corrections, which are checked against primary sources before any update.
\n","outroMarkdown":null,"outroHtml":null,"contentJson":{},"configJson":{},"noteMarkdown":"This answer was written and reviewed by the AnswerStack Editorial Team, which has no commercial stake in the products, companies, or methods discussed. Every claim is cited inline and verified on the dates shown.","noteHtml":"This answer was written and reviewed by the AnswerStack Editorial Team, which has no commercial stake in the products, companies, or methods discussed. Every claim is cited inline and verified on the dates shown.
\n","sortOrder":8}],"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":"PSTN defined as the aggregate of operator-run telephone networks; circuit switching with a dedicated path per call; digital core using PCM and 64 kbit/s DS0 channels; originally analog, now predominantly digital in the core with analog only on the local loop; POTS as the analog access method to the ","domain":"en.wikipedia.org","publisherName":"Wikipedia"},{"title":"Plain old telephone service","url":"https://en.wikipedia.org/wiki/Plain_old_telephone_service","excerpt":"Plain old telephone service (POTS) ... is a retronym for voice-grade telephone service that employs analog signal transmission over copper loops.","quoteText":null,"sourceRole":"INDEPENDENT","verifiedAt":"2026-07-18T00:00:00","supportsText":"POTS as a retronym for analog voice-grade telephone service over copper loops; the voice band; the copper subscriber loop; loop power at about 48 volts backed by central-office batteries so service continues during a customer power interruption; POTS as a service delivered over the PSTN; ISDN and Vo","domain":"en.wikipedia.org","publisherName":"Wikipedia"},{"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":"Plain Old Telephone Service (POTS) refers to the traditional, analog voice transmission phone system implemented over physical copper wires (twisted pair).","quoteText":null,"sourceRole":"INDEPENDENT","verifiedAt":"2026-07-18T00:00:00","supportsText":"POTS as traditional analog voice over twisted-pair copper; the limited voice frequency band of about 300 to 3,400 Hz; POTS as the basic telephone service used since the early days of the telephone; copper cannot carry high-bandwidth signals","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.","quoteText":null,"sourceRole":"INDEPENDENT","verifiedAt":"2026-07-18T00:00:00","supportsText":"PSTN as the world's interconnected circuit-switched telephone networks; switches acting as nodes; subscriber lines connecting to local, trunk, main, and central exchanges; the industry transition from PSTN to all-IP; the PSTN also being called plain old telephone service","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 technology and service, while PSTN refers to the entire public switched telephone network itself, which now includes digital components.","quoteText":null,"sourceRole":"INDEPENDENT","verifiedAt":"2026-07-18T00:00:00","supportsText":"POTS as the analog technology and service versus the PSTN as the whole network that now includes digital components; the copper sunset and rising cost of maintaining aging copper; the FCC clearing carriers such as AT&T and Verizon to move customers off copper to fiber and wireless","domain":"nextiva.com","publisherName":"Nextiva"},{"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 of voice frequencies, the baseline digital voice channel of the telephone network sampled at 8 kHz to a 64 kbit/s stream; in force","domain":"itu.int","publisherName":"International Telecommunication Union (ITU-T)"},{"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; the analog copper network is moving to All-IP delivered as Voice over IP over broadband; Openreach is withdrawing legacy products and has stopped selling new copper-based lines","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":"The analog network has reached the end of its serviceable life; industry-led migration to VoIP expected to be substantially complete by the end of January 2027; a power-resilience requirement that customers can reach emergency services for at least one hour during a power cut, usually via a battery ","domain":"gov.uk","publisherName":"GOV.UK"},{"title":"POTS Phone Line Replacement: Everything Businesses Need to Know","url":"https://www.atlantech.net/blog/pots-in-a-box-pots-replacement","excerpt":"POTS stands for Plain Old Telephone Service, those traditional analog copper lines used for decades to support voice calls, fax machines, security systems, fire panels, elevator phones, and more.","quoteText":null,"sourceRole":"SUPPORTING","verifiedAt":"2026-07-18T00:00:00","supportsText":"POTS as traditional analog copper lines that still carry voice, fax, alarm, fire-panel, and elevator circuits; FCC deregulation removing the requirement to maintain copper; carriers decommissioning copper and adding surcharges that raise the price of remaining POTS lines. Corroborated by [5] and [4]","domain":"atlantech.net","publisherName":"Atlantech Online"}],"revisions":[],"relatedAnswers":[{"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":"2026-07-20T16:01:27.137","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":"Standard PSTN calls are unencrypted, so they are exposed to line taps, interception inside the exchange (which carriers are legally required to support), and SS7 signaling attacks that can redirect calls and track users. The network supplies no encryption of its own. Confidentiality is possible only by adding matched crypto devices at both ends, such as STU-III or STE secure phones, or by carrying the call over encrypted IP using SRTP and TLS. Encryption always lives at the endpoints, never in the PSTN itself.","url":"/q/is-pstn-secure-and-can-pstn-calls-be-encrypted"},{"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":"2026-07-20T16:01:24.898","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":"When copper POTS lines move to VoIP, the equipment that fails is the kind that dials out as data or reaches for help automatically: fire alarm panel communicators, elevator emergency phones, burglar alarm dialers, medical alert pendants, fax machines, and card-payment terminals. They break because packet networks compress and drop the exact tones these machines depend on, and because a VoIP line loses power in an outage that a copper loop survived. Each one needs a cellular, IP, or analog-emulating replacement before its line is cut.","url":"/q/which-legacy-devices-are-still-at-risk-when-pstn-pots-lines-are-retired-or"},{"id":"28c898f5-b2d9-4a9d-88be-bd46bb9848e9","slug":"what-is-a-pstn-gateway-and-what-do-fxs-and-fxo-ports-do","question":"What is a PSTN gateway, and what do FXS and FXO ports do?","publishedAt":"2026-07-20T16:01:22.747","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":"A PSTN gateway bridges the traditional phone network and a VoIP system by converting analog or TDM voice into IP packets and back. Its analog ports come in two types: an FXS port powers and rings an end device like a phone or fax, and an FXO port connects to a live phone line from the PSTN or a PBX. FXS and FXO always pair, one feeding the line the other receives.","url":"/q/what-is-a-pstn-gateway-and-what-do-fxs-and-fxo-ports-do"},{"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":"2026-07-18T15:32:04.773","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, carrier-run network that connects phones worldwide; a PBX is a private switch that routes calls inside one organization and shares a few outside lines among many users. They are not rivals. A PBX plugs into the PSTN through trunk lines so staff can reach outside numbers, which is how a 100-person office runs on about ten external lines. Today most PBXs are IP or cloud-hosted and connect to the PSTN over a SIP trunk.","url":"/q/what-is-the-difference-between-pstn-and-pbx"}],"contributorStats":{"verifiedAnswers":224,"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":"2026-07-18T15:32:02.968","author":{"@type":"Person","name":"AnswerStack Editorial Team","worksFor":{"@type":"Organization","name":"AnswerStack"},"url":"https://www.answerstack.io/contributors/answer-stack"},"about":[{"@type":"Thing","name":"PSTN"},{"@type":"Thing","name":"Telecommunications"}],"acceptedAnswer":{"@type":"Answer","text":"The difference is one of scope: the public switched telephone network, or PSTN, is the entire interconnected system of operator-run telephone networks, while plain old telephone service, or POTS, is the basic analog voice service delivered to a subscriber over that system.[1][2] POTS is therefore a service that runs on the PSTN, not a separate network, which is why the two names often get used for the same thing.[2][4] Technically, POTS is analog from end to end over a copper pair and limited to a narrow voice band of roughly 300 to 3,400 hertz, whereas the PSTN's core has been digital for decades, encoding each call as a 64 kbit/s stream.[1][3][6] Both are now being retired together as carriers move voice onto internet protocol networks, and the United Kingdom is scheduled to switch off its PSTN, and the POTS lines it carries, by 31 January 2027.[7][8]","url":"https://www.answerstack.io/q/what-is-the-difference-between-pstn-and-pots","upvoteCount":0,"datePublished":"2026-07-18T15:32:02.968","dateModified":"2026-07-18T00:00:00","author":{"@type":"Person","name":"AnswerStack Editorial Team","worksFor":{"@type":"Organization","name":"AnswerStack"},"url":"https://www.answerstack.io/contributors/answer-stack"},"citation":[{"@type":"CreativeWork","name":"Public switched telephone network","url":"https://en.wikipedia.org/wiki/Public_switched_telephone_network"},{"@type":"CreativeWork","name":"Plain old telephone service","url":"https://en.wikipedia.org/wiki/Plain_old_telephone_service"},{"@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"},{"@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":"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"},{"@type":"CreativeWork","name":"POTS Phone Line Replacement: Everything Businesses Need to Know","url":"https://www.atlantech.net/blog/pots-in-a-box-pots-replacement"}]}}}