Core Concepts
PSTN (Public Switched Telephone Network)
By Myroslav Orshak · operates licensed carrier infrastructure · Updated September 2026
The PSTN (Public Switched Telephone Network) is the traditional global telephone network: the connected system of copper lines, fiber, and switching centers that has carried calls since the days of operators. Every phone number still ultimately connects to it.
How it works
When people say 'a phone line,' they historically meant a PSTN connection: a dedicated circuit from your building to the phone company's switching office. Dial a number and the network reserves a path between the two ends for the whole conversation — one call, one circuit, end to end. That circuit-based design is why the old network was so consistent, and also why it was so expensive to scale: capacity had to exist physically for every simultaneous call.
The PSTN is still the connective tissue of phone numbers. When your internet-based phone system calls a mobile phone or an old landline, your provider hands the call to the PSTN, which delivers it the last stretch. That handoff is why any phone can call any other phone regardless of the technology on either end — and it is happening less each year as both ends of more calls become internet-based.
Why it matters
Because it is being switched off, piece by piece. US carriers have been retiring the copper portions of the PSTN with regulatory approval since 2017, and the calls themselves increasingly travel the internet even when a copper line is involved somewhere. For a business, the PSTN matters mostly as a deadline: services that depend on it — analog lines, older alarm circuits, fax over copper — are on borrowed time, and the prices for what remains climb every year.
The FCC streamlined copper retirement in 2017, letting carriers withdraw traditional phone service area by area with notice. That is why remaining business copper lines are commonly quoted at $50 to $100 or more a month, and why many carriers no longer take new copper orders.
Related terms
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See what replaces a landline →Frequently asked questions
Is the PSTN the same thing as a landline?
Close. A landline is your individual connection; the PSTN is the giant network it plugs into. In everyday speech the terms blur together, and for most practical purposes 'the PSTN is being retired' and 'landlines are going away' mean the same thing for your business.
Is the PSTN shutting down completely?
The copper access part is genuinely being retired in the US, area by area, and several other countries have announced full switch-off dates. Phone numbers and the routing between carriers live on — calls just travel as internet data instead of dedicated circuits. Your number survives; the copper wire it once lived on does not.
Can my VoIP phone call a PSTN number?
Yes — that interconnection is the whole point. Your provider bridges calls between the internet and the traditional network automatically, which is why an internet-based business line can call any landline or mobile phone and receive calls from them with nothing special on your end.
What should a business still on the PSTN do?
Treat it as a migration with a deadline you don't control. Move your numbers to an internet-based service on your own schedule, and move fax to an email-based service. Before touching the genuine exceptions, check their certification rules: elevator phones, fire alarm panels, and some medical alert devices may require analog lines.