What Is PSTN? Public Switched Telephone Network
The 150-year-old global grid that still connects every regular phone number on Earth.
The PSTN (Public Switched Telephone Network) is the worldwide circuit-switched network of copper wires, fiber optic cables, switching centers, and carrier interconnections that has connected telephone numbers globally for over a century. It is the physical and logical infrastructure that makes a phone number work universally: dial a number in any country, and the PSTN routes the call through a chain of carriers to ring that specific device — whether it's a landline in a Shenzhen factory or a mobile phone in İstanbul.
How the PSTN works
When you dial a phone number, the PSTN performs a series of routing decisions:
- Number analysis. The network reads the country code (e.g., +86 for China), then the area/city code, then the subscriber number. Each segment narrows the route.
- Circuit establishment. In the traditional PSTN, a dedicated electrical circuit is established between the caller and the recipient. This circuit-switched model means the line is yours — and you're billed — for the entire duration of the call, whether you're speaking or silent.
- Carrier handoff. International calls hop between carriers — your local carrier hands off to a long-distance carrier, which hands off to the destination country's carrier, which terminates the call to the recipient's device. Each handoff adds latency and cost.
- Termination. The destination carrier rings the recipient's device and bridges the audio path.
PSTN vs. VoIP: the shift
The PSTN is circuit-switched — a dedicated path for each call. VoIP is packet-switched — your voice shares the same IP network as your email and web traffic. The economic difference is dramatic:
- PSTN international calling costs carriers ~$0.01–$0.05/min to terminate a call, with consumer prices often 5–20× higher after carrier markup.
- VoIP reduces the IP-transport portion to near-zero cost; only the PSTN termination leg (connecting the VoIP network to the recipient's phone) incurs a per-minute carrier fee.
- This is why VoIP international calling can cost $0.02–$0.10/min while traditional carrier rates are $0.50–$3.00/min.
The PSTN is shrinking — but not gone
Several countries — including the UK, Germany, and Australia — have announced plans to sunset their copper PSTN infrastructure entirely. The UK's PSTN switch-off is scheduled for 2027, after which all voice calls in the UK will be carried over IP. However, the PSTN remains the backbone of global phone number reachability: even VoIP calls ultimately terminate to the PSTN when the recipient is a regular phone number. A browser-based calling service like AKITAKI uses VoIP (WebRTC) for the caller's side but still relies on PSTN carrier partners to ring the destination phone.
How AKITAKI connects to the PSTN
When you make a call on AKITAKI, your voice starts as a WebRTC stream in your browser, travels over the internet to Telnyx (our carrier partner), which operates a global PSTN interconnection fabric. Telnyx terminates the call to the destination country's carrier, which delivers it to the recipient's mobile or landline. You get the cost structure of VoIP (per-minute rates from ~$0.02/min) with the universal reach of the PSTN (any phone number in 180+ countries). Read more about WebRTC →