PSTN
The Public Switched Telephone Network — the traditional circuit-switched phone system.
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The PSTN is the Public Switched Telephone Network: the aggregate of circuit-switched telephone networks that has carried voice calls for more than a century, using copper lines, fibre, and switching centres.
A traditional landline is a direct PSTN connection. VOIP calls travel over the internet instead and only touch the PSTN when a call needs to reach a number that still lives on it, which happens through a gateway.
The distinction shows up in line-type data. PSTN landlines cannot receive SMS, which is the practical reason a contact list mixing landlines and mobiles will underperform until the two are separated.
Related terms and concepts
- SIP trunk — A virtual connection that carries voice calls over the internet instead of physical phone lines.
- Line type — The classification of a phone number as mobile, landline, VOIP, or invalid.
- DID (Direct Inward Dialing) — A phone number that routes directly to a specific extension or user, bypassing a receptionist.
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