What is PRI Line?

A PRI line is the legacy digital trunk that delivered 23 phone lines over one circuit — the standard business connection before SIP trunking.

PRI (Primary Rate Interface) is the legacy digital circuit that carried 23 voice channels over one physical line — how mid-size businesses bought “23 phone lines at once” for decades, feeding on-prem PBXes.

Why you still see the term

PRIs are being replaced by SIP trunking (same job, over the internet, a fraction of the cost) and by POTS replacement for special circuits. If a provider quotes you a new PRI in 2026, ask why — but if you have one, its renewal date is your best negotiating leverage: incumbents discount heavily to keep PRI revenue from walking to SIP.

Related terms:
sip trunkingpots replacementvoip

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