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Get Prices → 📞 0121 268 0121A SIP trunk is a virtual phone line that runs over your internet connection. Instead of plugging physical telephone cables into a wall socket connected to BT's network, SIP trunks send your calls as data packets over your broadband.
The "SIP" stands for Session Initiation Protocol — the technical standard that controls how voice calls start, connect and end over IP networks. The "trunk" is an old telecoms term for a group of lines (traditionally a bundle of phone lines connecting an office PBX to the public network).
This is where most people get confused. Both use the internet to make calls, but they work differently:
A SIP trunk is a virtual phone line that runs over your internet connection. Instead of plugging physical telephone cables into a wall socket connected to BT's network, SIP trunks send your calls as data packets over your broadband.
The "SIP" stands for Session Initiation Protocol — the technical standard that controls how voice calls start, connect and end over IP networks. The "trunk" is an old telecoms term for a group of lines (traditionally a bundle of phone lines connecting an office PBX to the public network).
This is where most people get confused. Both use the internet to make calls, but they work differently:
A "channel" = one simultaneous call. For most offices, you need roughly 1 channel per 3–4 users for typical call patterns.
Most modern IP-capable PBX systems support SIP. However, if your PBX was installed before 2010, it may not support SIP without an adapter (ISDN gateway). Before ordering SIP trunks, confirm with your PBX supplier or installer that the system is SIP-compatible.
Telexico provides SIP trunks for businesses across the UK, with number porting included. Get a quote in 24 hours.
Explore Telexico's VoIP Phone Systems service or read related guides:
| SIP Trunks | Hosted VoIP | |
|---|---|---|
| What you provide | Your own on-premise PBX hardware | Nothing — it's all in the cloud |
| Monthly cost per channel | £3–£8 | £10–£20/user |
| Setup complexity | High (PBX config required) | Low (plug and play) |
| Best for | Businesses with existing PBX | New setups or PSTN migration |
| Hardware required | IP-compatible PBX | IP phones or softphones only |
| Scalability | Add channels manually | Add users instantly |
| Channels | Monthly Cost | Included Minutes |
|---|---|---|
| 2 channels | £15–£25 | Unlimited UK calls |
| 5 channels | £30–£50 | Unlimited UK calls |
| 10 channels | £55–£90 | Unlimited UK calls |
| 20 channels | £100–£160 | Unlimited UK calls + CLI routing |
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"Switched our entire office phone system and broadband. The team handled everything, zero downtime. Saving over £200 a month compared to our old BT contract."
"Had failover installed after losing internet for a whole day. Assure X kicks in within seconds. Our team didn't even notice when the main line dropped last week."
"Our dental practice needed reliable phones and fast broadband. Telexico sorted everything in one visit. The AI receptionist handles after-hours calls brilliantly."
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