The PSTN is the public telephone network that lets a phone number on one carrier reach a number on another. A PBX is the phone system one organization runs for itself. It gives people extensions and decides how calls are routed, answered and transferred. A business normally uses both, because the PBX handles calls inside the organization and a PSTN connection carries calls to and from outside phone numbers.
\n","summary":"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.","publishedAt":"2026-09-19T15:32:04.773","verifiedAt":"2026-07-18T00:00:00","editorialStatus":"APPROVED","lastReviewedAt":"2026-10-10T03:12:20.323","nextReviewDueAt":"2026-10-18T00:00:00","templateVersion":"v2","aliases":["PSTN vs PBX","PBX vs PSTN","What is the difference between a PBX and the PSTN?","How does a PBX connect to the PSTN?","Is a PBX the same as the PSTN?","Public switched telephone network vs private branch exchange","Difference between a business phone system and the public phone network","PBX and PSTN explained","How are the PSTN and a PBX related?","PSTN and PBX meaning","Do I need a PBX or just 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":"a229503b-dd75-49f4-9753-896da2da0330","sectionKey":"public_and_private","sectionType":"markdown_section","heading":"A public network and a private phone system","introMarkdown":"PSTN stands for [public switched telephone network](https://www.answerstack.io/q/what-is-the-pstn-public-switched-telephone-network). It is public in the sense that many carriers take part and connect to each other, so a number on one can be dialed from another.\n\nPBX stands for private branch exchange, and the word private carries the meaning. A PBX serves one organization, and that organization sets its rules. Microsoft describes its own product in these terms. [Teams Phone](https://learn.microsoft.com/en-us/microsoftteams/what-is-phone-system-in-office-365) is its technology for \"call control and Private Branch Exchange (PBX) capabilities in the Microsoft 365 cloud.\" Call control means deciding what happens to a call. It covers which phone rings, what a caller hears after hours and where a call goes when nobody answers.\n\nThe feature list of a hosted PBX shows the same job. Atlantech Online's [business phone service](https://www.atlantech.net/solutions/voice/phone) includes auto attendants, ACD groups that distribute calls among staff, a receptionist console and voicemail transcription. An administrator can add users, devices and call queues. Each item on that list is about handling calls for one organization. Delivering a call to another company's number is a different job, and it belongs to the PSTN side.","introHtml":"PSTN stands for public switched telephone network. It is public in the sense that many carriers take part and connect to each other, so a number on one can be dialed from another.
\nPBX stands for private branch exchange, and the word private carries the meaning. A PBX serves one organization, and that organization sets its rules. Microsoft describes its own product in these terms. Teams Phone is its technology for "call control and Private Branch Exchange (PBX) capabilities in the Microsoft 365 cloud." Call control means deciding what happens to a call. It covers which phone rings, what a caller hears after hours and where a call goes when nobody answers.
\nThe feature list of a hosted PBX shows the same job. Atlantech Online's business phone service includes auto attendants, ACD groups that distribute calls among staff, a receptionist console and voicemail transcription. An administrator can add users, devices and call queues. Each item on that list is about handling calls for one organization. Delivering a call to another company's number is a different job, and it belongs to the PSTN side.
\n","outroMarkdown":null,"outroHtml":null,"contentJson":{},"configJson":{},"noteMarkdown":null,"noteHtml":null,"sortOrder":10},{"id":"d4eb7c30-caa0-447e-93ad-95651a1d3f0c","sectionKey":"side_by_side","sectionType":"table_section","heading":"PSTN and PBX side by side","introMarkdown":null,"introHtml":null,"outroMarkdown":null,"outroHtml":null,"contentJson":{"rows":[{"cells":["Who it serves","Anyone with a phone number","One organization"]},{"cells":["What it does","Carries calls between carriers and their numbers","Routes calls among the organization's users and applies its call rules"]},{"cells":["How you reach someone","A full public phone number","An extension, or a public number assigned to that user"]},{"cells":["Who runs it","Telephone carriers","The organization, or a provider hosting it for the organization"]}],"columns":["Question","PSTN","PBX"]},"configJson":{},"noteMarkdown":null,"noteHtml":null,"sortOrder":20},{"id":"ebc81c02-7f1b-405c-bd8c-5ee2548f1496","sectionKey":"two_calls","sectionType":"markdown_section","heading":"Two calls from the same desk","introMarkdown":"Suppose a 20-person accounting firm uses a cloud PBX. An employee at extension 104 calls a colleague at extension 117. The PBX recognizes both extensions as its own users and connects them. The call needs no public phone number, and no carrier handoff is involved. Microsoft describes the same behavior in Teams, where calls between users in one organization are, by default, handled inside Teams and stay off the PSTN.\n\nThat does not mean the call stays inside the building. In this firm, both phones reach the provider over the office internet connection, so the call depends on that connection.\n\nNow the same employee dials a supplier's ten-digit number. The PBX sees that the number is not one of its own and sends the call out through the firm's PSTN connection. The carrier on that connection passes it toward the supplier's carrier, and the supplier's phone rings. The PBX chose to send the call out, and the PSTN delivered it.\n\nIncoming calls run the other way. The carrier delivers a call for the firm's main number, and the PBX decides whether the auto attendant answers or a desk phone rings.","introHtml":"Suppose a 20-person accounting firm uses a cloud PBX. An employee at extension 104 calls a colleague at extension 117. The PBX recognizes both extensions as its own users and connects them. The call needs no public phone number, and no carrier handoff is involved. Microsoft describes the same behavior in Teams, where calls between users in one organization are, by default, handled inside Teams and stay off the PSTN.
\nThat does not mean the call stays inside the building. In this firm, both phones reach the provider over the office internet connection, so the call depends on that connection.
\nNow the same employee dials a supplier's ten-digit number. The PBX sees that the number is not one of its own and sends the call out through the firm's PSTN connection. The carrier on that connection passes it toward the supplier's carrier, and the supplier's phone rings. The PBX chose to send the call out, and the PSTN delivered it.
\nIncoming calls run the other way. The carrier delivers a call for the firm's main number, and the PBX decides whether the auto attendant answers or a desk phone rings.
\n","outroMarkdown":null,"outroHtml":null,"contentJson":{},"configJson":{},"noteMarkdown":null,"noteHtml":null,"sortOrder":30},{"id":"a6cc1c39-620f-4035-8358-14852bbc6abf","sectionKey":"hosted_pbx_needs_pstn","sectionType":"markdown_section","heading":"A hosted PBX still needs a PSTN connection","introMarkdown":"Buying a PBX as a cloud service can make the two functions look like one product. Microsoft keeps them visibly apart. Its documentation states that PSTN connectivity is separate from the Teams Phone license. The license gives a user the calling features. A separate arrangement supplies the phone numbers and the access to outside calling. A company with only the license can call coworkers in Teams, but it cannot dial an outside phone number. We cover the choices in [how to choose a PSTN connectivity option for Teams Phone](https://www.answerstack.io/q/how-do-i-choose-a-pstn-connectivity-option-for-teams-phone).\n\nA carrier can also sell both together. Atlantech's page offers two routes. A customer can use its cloud PBX, or keep its own PBX and take service over SIP, PRI or analog. On the first route, Atlantech supplies the PBX and the public connection as one service, and the page says its hosted voice includes unlimited nationwide calling. On the second route, the customer keeps its own PBX and buys only the connection, delivered in whichever of those forms the PBX accepts. We compare the two routes in [SIP trunking versus cloud PBX](https://www.answerstack.io/q/what-is-the-difference-between-sip-trunking-and-cloud-pbx), and using SIP trunking with an existing phone system covers the second one.\n\nA bundle is convenient, and both functions are still inside it. Knowing that helps when you compare quotes. Atlantech prices its phone service by consultation and publishes no rate on that page. So read a quote from it, or from any provider, for both parts: the phone system features and the public calling that comes with them.","introHtml":"Buying a PBX as a cloud service can make the two functions look like one product. Microsoft keeps them visibly apart. Its documentation states that PSTN connectivity is separate from the Teams Phone license. The license gives a user the calling features. A separate arrangement supplies the phone numbers and the access to outside calling. A company with only the license can call coworkers in Teams, but it cannot dial an outside phone number. We cover the choices in how to choose a PSTN connectivity option for Teams Phone.
\nA carrier can also sell both together. Atlantech's page offers two routes. A customer can use its cloud PBX, or keep its own PBX and take service over SIP, PRI or analog. On the first route, Atlantech supplies the PBX and the public connection as one service, and the page says its hosted voice includes unlimited nationwide calling. On the second route, the customer keeps its own PBX and buys only the connection, delivered in whichever of those forms the PBX accepts. We compare the two routes in SIP trunking versus cloud PBX, and using SIP trunking with an existing phone system covers the second one.
\nA bundle is convenient, and both functions are still inside it. Knowing that helps when you compare quotes. Atlantech prices its phone service by consultation and publishes no rate on that page. So read a quote from it, or from any provider, for both parts: the phone system features and the public calling that comes with them.
\n","outroMarkdown":null,"outroHtml":null,"contentJson":{},"configJson":{},"noteMarkdown":null,"noteHtml":null,"sortOrder":40},{"id":"2ed39e95-8c18-4efd-8bd2-8e6a5039216b","sectionKey":"older_meanings","sectionType":"markdown_section","heading":"Older meanings that no longer hold","introMarkdown":"Both terms picked up assumptions from the equipment that used to deliver them. A PBX was once a cabinet in the office, so people expect it to be on the premises. It can be, and it can also run in a provider's data center. A cloud PBX takes the PBX out of the office. The office still needs working power and a working network for its phones to reach the service, which is one of the trade-offs in [how UCaaS compares to an on-premises PBX](https://www.answerstack.io/q/how-does-ucaas-compare-to-on-premises-pbx).\n\nFor decades a fixed line reached the PSTN over copper, so people expect the word to mean copper. Some carriers are now retiring that copper, and public-number calling continues over IP connections.\n\nAn older PBX can stay in service through that change. If it has analog or digital trunk ports, a [PSTN gateway](https://www.answerstack.io/q/what-is-a-pstn-gateway-and-what-do-fxs-and-fxo-ports-do) can join it to an IP connection by converting calls between telephone circuits and IP packets.","introHtml":"Both terms picked up assumptions from the equipment that used to deliver them. A PBX was once a cabinet in the office, so people expect it to be on the premises. It can be, and it can also run in a provider's data center. A cloud PBX takes the PBX out of the office. The office still needs working power and a working network for its phones to reach the service, which is one of the trade-offs in how UCaaS compares to an on-premises PBX.
\nFor decades a fixed line reached the PSTN over copper, so people expect the word to mean copper. Some carriers are now retiring that copper, and public-number calling continues over IP connections.
\nAn older PBX can stay in service through that change. If it has analog or digital trunk ports, a PSTN gateway can join it to an IP connection by converting calls between telephone circuits and IP packets.
\n","outroMarkdown":null,"outroHtml":null,"contentJson":{},"configJson":{},"noteMarkdown":null,"noteHtml":null,"sortOrder":50}],"citations":[{"title":"What is a private branch exchange (PBX)?","url":"https://www.techtarget.com/searchunifiedcommunications/definition/private-branch-exchange","excerpt":"A private branch exchange (PBX) is a telephone system within an enterprise that switches calls between users on local lines, while enabling all users to share a certain number of external phone lines.","quoteText":null,"sourceRole":"INDEPENDENT","verifiedAt":"2026-07-18T00:00:00","supportsText":"PBX switches calls between internal users while sharing a limited number of external phone lines; saves the cost of a line per user to the central office; trunk lines terminate at the PBX; traditional analog, IP, and hosted PBX types","domain":"techtarget.com","publisherName":"Informa TechTarget"},{"title":"Business telephone system","url":"https://en.wikipedia.org/wiki/Business_telephone_system","excerpt":"The central office lines provide connections to the public switched telephone network (PSTN) and the concentration aspect of a PBX permits the shared use of these lines between all stations in the organization.","quoteText":null,"sourceRole":"INDEPENDENT","verifiedAt":"2026-07-18T00:00:00","supportsText":"PBX is privately owned and operated; central office lines connect it to the PSTN and are shared across stations by concentration; each device is an extension with an extension number; VoIP and hosted PBX developments in the 1990s","domain":"en.wikipedia.org","publisherName":"Wikipedia"},{"title":"PBX Systems for Business Efficiency: A Primer","url":"https://www.mitel.com/articles/whats-the-meaning-of-pbx","excerpt":"a PBX allows a company to accommodate all its external voice communication requirements with a small number of external lines.","quoteText":null,"sourceRole":"INDEPENDENT","verifiedAt":"2026-07-18T00:00:00","supportsText":"A PBX lets a company meet its external voice needs with a small number of external lines; internal calls stay on the PBX; the switch routes many paths and shares limited outside lines efficiently","domain":"mitel.com","publisherName":"Mitel"},{"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 is the world's collection of interconnected circuit-switched public telephone networks; you connect to it as a carrier service; providers are transitioning from PSTN to all-IP; VoIP carries calls without circuit switching","domain":"techtarget.com","publisherName":"Informa TechTarget"},{"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 is the aggregate of operator-run telephone networks; uses circuit switching; large private company networks link to the PSTN only through limited gateways such as a large PBX","domain":"en.wikipedia.org","publisherName":"Wikipedia"},{"title":"Direct inward dialing","url":"https://en.wikipedia.org/wiki/Direct_inward_dial","excerpt":"the telephone company provides one or more trunk lines to the customer for connection to the customer's PBX, and allocates a range of telephone numbers to the customer.","quoteText":null,"sourceRole":"INDEPENDENT","verifiedAt":"2026-07-18T00:00:00","supportsText":"DID is a carrier service for PBX operators; the telephone company provides trunk lines and allocates a range of numbers; the dialed number is signaled to the PBX so a call routes to an extension without an operator; fewer circuits than DID numbers","domain":"en.wikipedia.org","publisherName":"Wikipedia"},{"title":"Centrex","url":"https://en.wikipedia.org/wiki/Centrex","excerpt":"It provides functions similar to a PBX, but is provisioned with equipment owned by, and located at, the telephone company premises.","quoteText":null,"sourceRole":"INDEPENDENT","verifiedAt":"2026-07-18T00:00:00","supportsText":"Centrex provides PBX-like functions but with equipment owned by and located at the telephone company, delivered from the central exchange rather than on the customer premises","domain":"en.wikipedia.org","publisherName":"Wikipedia"},{"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. Status: In force.","quoteText":null,"sourceRole":"PRIMARY","verifiedAt":"2026-07-18T00:00:00","supportsText":"E.164 is the international public telecommunication numbering plan governing public telephone numbers worldwide; maximum 15 digits with country codes; current version in force","domain":"itu.int","publisherName":"International Telecommunication Union (ITU-T)"},{"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 PSTN has reached the end of its serviceable life; the industry is upgrading landline services to digital technology using an internet connection such as VoIP and All-IP telephony","domain":"gov.uk","publisherName":"GOV.UK"},{"title":"SIP Trunking vs. Hosted PBX: 5 Key Differences","url":"https://www.atlantech.net/blog/sip-trunking-vs.-hosted-pbx-whats-the-difference","excerpt":"SIP Trunking uses IP at the application layer to connect a phone call to the Public Switched Telephone Network (PSTN), replacing a traditional 'phone trunk' such as a Primary Rate Interface (PRI) or analog line.","quoteText":null,"sourceRole":"SUPPORTING","verifiedAt":"2026-07-18T00:00:00","supportsText":"A SIP trunk connects a PBX to the PSTN over IP, replacing a traditional phone trunk such as a PRI or analog line; corroborated by [2] on IP and hosted PBX connectivity","domain":"atlantech.net","publisherName":"Atlantech Online"}],"revisions":[{"revisedAt":"2026-07-18T15:32:04.773+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":"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 difference between PSTN and PBX?","text":"What is the difference between PSTN and PBX?","url":"https://www.answerstack.io/q/what-is-the-difference-between-pstn-and-pbx","answerCount":1,"datePublished":"2026-09-19T15:32:04.773","about":[{"@type":"Thing","name":"PSTN"},{"@type":"Thing","name":"Telecommunications"}],"acceptedAnswer":{"@type":"Answer","text":"The PSTN is the public telephone network that lets a phone number on one carrier reach a number on another. A PBX is the phone system one organization runs for itself. It gives people extensions and decides how calls are routed, answered and transferred. A business normally uses both, because the PBX handles calls inside the organization and a PSTN connection carries calls to and from outside phone numbers.","url":"https://www.answerstack.io/q/what-is-the-difference-between-pstn-and-pbx","upvoteCount":0,"datePublished":"2026-09-19T15:32:04.773","dateModified":"2026-07-18T00:00:00","citation":[{"@type":"CreativeWork","name":"What is a private branch exchange (PBX)?","url":"https://www.techtarget.com/searchunifiedcommunications/definition/private-branch-exchange"},{"@type":"CreativeWork","name":"Business telephone system","url":"https://en.wikipedia.org/wiki/Business_telephone_system"},{"@type":"CreativeWork","name":"PBX Systems for Business Efficiency: A Primer","url":"https://www.mitel.com/articles/whats-the-meaning-of-pbx"},{"@type":"CreativeWork","name":"PSTN (public switched telephone network)","url":"https://www.techtarget.com/searchnetworking/definition/PSTN"},{"@type":"CreativeWork","name":"Public switched telephone network","url":"https://en.wikipedia.org/wiki/Public_switched_telephone_network"},{"@type":"CreativeWork","name":"Direct inward dialing","url":"https://en.wikipedia.org/wiki/Direct_inward_dial"},{"@type":"CreativeWork","name":"Centrex","url":"https://en.wikipedia.org/wiki/Centrex"},{"@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":"UK transition from analogue to digital landlines","url":"https://www.gov.uk/guidance/uk-transition-from-analogue-to-digital-landlines"},{"@type":"CreativeWork","name":"SIP Trunking vs. Hosted PBX: 5 Key Differences","url":"https://www.atlantech.net/blog/sip-trunking-vs.-hosted-pbx-whats-the-difference"}]}}}