PSTN: What Does It Mean?

The global circuit-switched network behind every landline and POTS-line phone call, including fax.

作者

莎拉·米切尔

发布于

September 9, 2026

最后更新于

September 11, 2026

The PSTN (Public Switched Telephone Network) is the global circuit-switched network that connects landlines, POTS lines, and traditional fax calls.
A traditional fax call is routed through the PSTN the same way a voice phone call is, using the same switching infrastructure.
Fax.Plus faxes still reach a traditional recipient through the PSTN when needed, but the sender never has to connect to it directly.

What Is the PSTN?

The PSTN (Public Switched Telephone Network) is the global circuit-switched network that connects landlines, POTS lines, and traditional phone calls to each other, regardless of which local provider or country they're on. It's the infrastructure layer underneath the phone call itself, not a service a person subscribes to directly.

How a Traditional Fax Call Uses the PSTN

A traditional fax call is routed through the PSTN the exact same way a voice phone call is, using the same switching infrastructure to connect the sender's line to the recipient's. This applies whether the call originates from an individual landline, each individual POTS line, or, less commonly today, a digital ISDN connection.

Does Fax.Plus Use the PSTN?

Fax.Plus faxes are sent over the internet on the sending side, but a fax reaching a recipient who still uses a traditional phone-connected machine ultimately completes its final leg over the PSTN, the same way any call to that number would. The sender never has to connect to the PSTN directly, that part is handled entirely behind the scenes. See leaving the PSTN behind entirely for more on that shift.

A Common Case: Consolidating Fax Lines Across Store Locations

A large retail chain based in Tennessee operates dozens of store locations, each historically dialing out over its own local PSTN connection to fax paperwork back to headquarters. Moving every location onto Fax.Plus replaces those individual phone lines with a single shared account, while faxes to outside partners still reach the PSTN exactly as before.

常见问题解答

Does the PSTN support fax, or only voice calls?

Both. The PSTN was built primarily for voice calls, but it also carries fax transmissions using the same switching infrastructure, since a fax call is routed no differently than a phone call.

Does Fax.Plus use the PSTN?

Fax.Plus sends faxes over the internet on the sending side. A fax reaching a recipient on a traditional phone-connected machine still completes its final leg over the PSTN.

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