Save Money with SIP Trunks

SIP (Session Initiation Protocol) Trunking is a way of connecting your business phone system to the public telephone network over the internet, instead of using traditional copper lines. A SIP Trunk is the virtual equivalent of a phone line: it carries multiple voice calls as data packets between your on-premise or hosted PBX and the PSTN. With IP Telecom, your SIP Trunk runs over our private, fully IP-based voice network - no VoIP gateways required - which delivers clearer audio and tighter security than converting analogue signals at the edge of your network.

A channel is the capacity to carry one simultaneous phone call. The number of channels you need is the maximum number of calls your team is likely to make or receive at the same time - not your total number of users. As a rough guide, a small office with 10-15 staff might only need 4-8 channels, while a busy contact centre may need 30 or more. IP Telecom offers fully flexible channel counts and you can burst extra channels during peak periods.

Analogue lines carry one call each over copper (which is soon to be phased out - see our Copper switch-off page for more information). ISDN2 (BRI) carries 2 calls, ISDN30 (PRI), E1 and T1 each carry up to 30 calls - but every additional line means more rental, more hardware and limited geographic flexibility. SIP Trunks replace all of these with a single IP connection that can scale up or down channel-by-channel, with no requirement for separate physical circuits per call. Because IP Telecom SIP Trunks are fully IP end-to-end, you also benefit from HD-quality audio and simpler, more resilient routing.

They are related but distinct. VoIP is the broad technology that carries voice over IP networks. SIP Trunking is a specific use of VoIP: it connects your existing phone system (PBX) to the outside world. Hosted PBX (also called Cloud PBX) is a fully cloud-hosted phone system provided as a service. IP Telecom offers both - and SIP Trunks work brilliantly with our Essentials Phone System, call centre platform, handsets and softphones, as well as with most leading third-party IP-PBXs.

In most cases, yes. IP Telecom SIP Trunks are interoperable with the vast majority of modern IP-PBX platforms, including SIP-enabled on-premise systems from leading vendors. We will confirm PBX compatibility, firmware version and licensing during the scoping phase so there are no surprises on cut-over day.

No. Because IP Telecom SIP Trunks are delivered end-to-end over IP, you do not need analogue VoIP gateways to convert the signal at your premises. If you are replacing analogue or ISDN lines, you simply enable the SIP functionality on your IP-enabled PBX (or move to the IP Telecom Essentials Phone System) and connect to our network over a standard internet or private IP connection.

Yes. We support full number portability: your existing geographic, non-geographic, DDI and freephone numbers can be ported to IP Telecom, so your customers, suppliers and staff keep calling the same numbers they always have. Our team manages the entire porting process on your behalf and coordinates the cut-over to minimise disruption.

Across Europe - and most aggressively in the UK where the PSTN and ISDN switch-off has been confirmed for January 2027 (with Northern Ireland set to be one of the first areas to shut off the PSTN network) - analogue and ISDN services are being switched off. Ireland is following the same all-IP direction - see our Copper Switch-Off page for more. If your business still relies on legacy copper or ISDN circuits, you will increasingly face support, supply and pricing pressure. Migrating to IP Telecom SIP Trunks now removes that risk and positions you to take advantage of lower call costs, better audio and easier remote-working on a future-proof platform.

IP Telecom SIP Trunks are priced on a simple pay-as-you-use basis, with a minute bundle. You pay only the calls you make outside of the minute bundle, with no hidden line-rental surprises. Because every customer’s call profile is different, we don’t publish a one-size-fits-all price list. To get a tailored figure, contact us or use the build your quote tool and our team will come back to you quickly.

No. IP Telecom does not charge setup fees and there are no fixed monthly subscription charges for the SIP Trunk you simply pay for what you use. This is one of the biggest cost benefits over analogue and ISDN line rental (something that is being phased out anyway – see our Copper Switch Off page for more), where you pay the same every month regardless of whether you actually use the line.

We offer flexible terms to suit your business - from rolling monthly arrangements through to longer-term commitments for customers who want to lock in volume pricing. Talk to our sales team about the option that best matches your usage profile and growth plans.

Yes. IP Telecom SIP Trunks support outbound international calling to a wide range of destinations at competitive per-minute rates. International tariffs vary by destination, so contact usor use the build-your-quote tool for the specific countries your team calls most.

Because SIP Trunks rely on your internet connection, resilience is critical. IP Telecom recommends - and can provide - a resilient internet setup (for example, a primary link plus a backup broadband or 4G/5G failover) so that if one path fails, calls automatically reroute via the other. Many of our customers also use IP Telecom’s cloud and failover options to keep call continuity across sites. We will design a resilience plan around your risk profile during the quoting stage.

Yes, when deployed correctly. As an ISO-accredited provider, IP Telecom implements industry best-practice security on our SIP platform, including access control, monitoring and the option of encrypted SIP (SIPS/TLS) and SRTP for signalling and media where your PBX supports it. This protects your voice traffic against interception and helps meet compliance requirements in regulated industries.

Because IP Telecom SIP Trunks carry voice fully over IP from end to end - with no analogue gateway conversions - audio quality is noticeably better than legacy lines. We further protect quality through QoS-aware routing on our private voice network, prioritised traffic on compatible IP connections and proper sizing of your internet bandwidth. Following a few simple LAN best practices (QoS marking, disabling SIP ALG, using a dedicated voice VLAN) keeps call quality consistently high.

Yes. One of the key advantages of SIP Trunking over fixed ISDN or analogue circuits is elastic capacity. If you are running a seasonal campaign, a conference call surge or a contact-centre peak, you can burst additional channels on demand. When the peak is over, channels can be reduced - and so can your costs. This makes SIP Trunks ideal for growing or seasonal businesses.

Yes. IP Telecom SIP Trunks work with our own IP Telecom Phone System, our cloud call-centre platform, IP handsets and softphones, and Microsoft Teams via our Teams-integrated voice solution. If you already have a compatible third-party PBX, handsets or contact-centre platform, we will confirm interoperability before deployment so you can keep the tools your teams already use.

Anywhere with a suitable internet connection. Because calls are carried over IP, your users can connect to the SIP Trunk from the office, a home setup, a branch site or while travelling - using IP handsets, softphones or our mobile apps. This makes IP Telecom SIP Trunks a strong fit for hybrid and multi-site organisations.