A brief history of VoIP, from dial-up to AI voice
How voice over IP evolved from early internet telephony to today's cloud and AI-powered business phone systems.
By the Telappliant team
Voice over IP has gone from a novelty for hobbyists to the default way UK businesses make and receive calls. Understanding how it got here explains why the PSTN switch-off in January 2027 is not a disruption, it is the last step of a journey that started decades ago.
The early experiments
The first practical internet voice calls date to the mid-1990s, when software like Vocaltec's Internet Phone let two PCs talk over a dial-up connection, at the cost of poor audio and the need for both parties to be online at the same time. It proved the concept but was nowhere near a business tool.
The 2000s: VoIP goes mainstream
- Broadband adoption made always-on, reasonable-quality calls realistic
- Skype (2003) brought free PC-to-PC calling to consumers
- SIP became the standard signalling protocol, letting hardware and software from different vendors interoperate
- Hosted PBX providers began offering business phone systems delivered entirely over the internet
The 2010s: cloud and mobility
As UK broadband speeds improved and 4G rolled out, VoIP moved from desk phones to softphone apps on laptops and mobiles. Cloud phone platforms took over from on-premise PBX hardware because they removed maintenance, scaled instantly and worked identically from any location.
The 2020s: the PSTN switch-off forces the issue
Openreach's decision to retire the analogue and ISDN network, completing by 31 January 2027, turned VoIP from an optional upgrade into the only supported way to make business calls. Every business still on analogue lines has had to move, which has made cloud voice the default rather than the exception.
Where VoIP is now
- Full fibre connectivity delivers call quality that dial-up-era engineers would not have believed possible
- Microsoft Teams Phone puts calling inside the same app as chat and meetings
- AI layers on top of cloud voice provide call summaries, sentiment analysis and automated receptionists
- SIP trunking still bridges legacy on-premise systems that have life left in them
What comes next
The trajectory points towards voice becoming one data stream among many inside a unified communications platform, with AI doing an increasing share of the routing, note-taking and follow-up that used to be manual. The technology that started as a hobbyist workaround now underpins how most UK businesses are reachable at all.
Next steps
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