POTS Line: What Is It?

The traditional analog phone-line service landlines and legacy fax machines run on, defined plainly.

Sarah Mitchell

Published on

September 9, 2026

Last updated on

November 3, 2026

POTS (Plain Old Telephone Service) is traditional analog telephone service, commonly delivered over copper wiring to landlines and legacy fax machines.
A POTS line supports one call at a time, including the fax call while a document is being transmitted.
Fax.Plus lets users fax online without maintaining an analog fax line or machine at their location; account, number and plan requirements still apply.

What Is a POTS Line?

POTS (Plain Old Telephone Service) is traditional analog telephone service, commonly delivered over copper wiring between a location and a local telephone exchange. An analog phone line of this type carries one call at a time, including the fax call while a document is being transmitted. It is the connection associated with a traditional home or office landline.

POTS vs. ISDN vs. PSTN

These terms describe related but distinct things. POTS is the analog telephone service; ISDN uses digital circuits; and PSTN names the public switched telephone network, rather than one particular customer-line service.

POTS Lines and Fax

Legacy fax machines were built to exchange fax tones through a telephone connection. A change to the line therefore needs a compatibility check for the actual fax machine and replacement service. Some setups retain the device through an analog telephone adapter; support depends on the equipment and provider.

Fax.Plus instead lets users send and receive faxes online without maintaining an analog fax line or physical fax machine at their location. This changes the office's sending and receiving workflow; it does not replace voice, alarm, elevator or emergency/911 connectivity using the old infrastructure. Plan, number and usage charges still need to be considered.

For the practical choice, costs to compare and number-transfer sequence, use the analog-to-digital fax migration plan. Keep the existing service active until any required number transfer is confirmed complete.

A Common Case: One POTS Line Doing One Job

Consider a mid-size consumer services company in Ohio that is still paying for a POTS line dedicated entirely to a fax machine nobody in the office uses anymore. It checks whether its fax number can be transferred to Fax.Plus, sets up the receiving workflow and verifies the confirmed transfer before closing the standalone analog fax line.

FAQs

What's the difference between POTS and PSTN?

POTS is the specific analog phone service delivered over copper wiring. PSTN is the larger circuit-switched network that POTS lines, along with other connection types, route through to reach their destination.

Is a POTS line the same as ISDN?

No. POTS is a specific analog service type, while ISDN is a separate digital alternative that carries voice, data, and fax over the same digital circuit.

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