The UK PSTN Switch-Off: What Hoteliers Need to Know

The UK’s traditional telephone network is approaching retirement. BT plans to close its Public Switched Telephone Network, or PSTN, by 31 January 2027, with services including traditional analogue lines and ISDN moving to digital, Internet Protocol-based alternatives.

For a hotel, this is not simply a project to replace the reception telephone line. PSTN and ISDN services can sit beneath the main hotel number, PBX trunks, lift emergency phones, alarm signalling, door entry, fax machines, payment equipment and other devices that may have been installed by different suppliers over many years.

The right response is not automatically “move everything to the cloud”. A modern cloud PBX may be ideal for one property, while another should retain or modernise an on-premises PBX and replace ISDN with SIP trunks. A third may need a hybrid design that preserves analogue guestroom phones and local survivability while adding cloud collaboration and central management.

This guide explains what is changing, how SIP trunks fit into the migration, how Alcatel-Lucent Enterprise cloud and on-premises platforms can help, and what to do with analogue extensions, lift phones and emergency alarm connections.

What is actually switching off—and when?

The key date for services using BT’s network is 31 January 2027. Ofcom’s current digital landline guidance confirms BT’s intention to retire the old network by that date. Providers operating their own networks may work to different programmes, so each service must be checked with the company that supplies it.

A national stop-sell took effect in September 2023. This meant providers could no longer order many new Wholesale Line Rental and PSTN-dependent services in the usual way. It did not mean every existing hotel line stopped working in 2023. The final retirement is the point that creates the urgent need to migrate remaining services.

“PSTN switch-off” is also not a precise synonym for “every copper cable is removed on the same day”. The withdrawal concerns the legacy services and switching platform. Some new digital services can still reach premises over copper access products, while full fibre is deployed progressively. Hotels should plan around the service they use—not make assumptions from the appearance of the cable entering the building.

BT Business lists PSTN, ISDN, ADSL and related WLR products among the services affected and warns that some business services cannot be migrated automatically. An unidentified line supporting a lift, alarm or old PBX therefore cannot safely be left for the carrier to resolve at the last moment.

Why hospitality properties are unusually exposed

Hotels often have a mixture of guest-facing, operational and safety-related communications. The main published number may arrive through ISDN channels into a PBX, while separate analogue lines have been ordered for lifts, fire or intruder alarm signalling, gates, plant telemetry or a fax machine. Billing may be split between the hotel, a management company, the building owner and individual maintenance providers.

The systems most likely to be missed include:

• Main telephone numbers, DDI ranges and ISDN channels connected to the hotel PBX.
• Passenger and service lift emergency phones, including lines billed separately from normal telephony.
• Fire, intruder, panic and building alarm signalling connected to an alarm receiving centre.
• Door entry, gate intercoms and refuge communications that dial external or internal destinations.
• Fax, franking, vending, EPOS and payment devices with dial-up or fallback modems.
• Backup lines and telemetry that are rarely used but expected to work during an incident.
• Remote buildings and staff accommodation with their own numbers or broadband-plus-line packages.

Government guidance on preparing estates for the switch-off highlights alarms, lift emergency lines, CCTV, door entry, tills, card machines and other specialist devices as potentially affected. The hospitality equivalent is a site-wide dependency audit involving IT, engineering, security, finance, the lift contractor, alarm maintainers and the incumbent telecoms provider.

SIP trunks: the practical replacement for ISDN

A SIP trunk is an IP-based voice service connecting a compatible PBX to a telephone carrier. It performs the external role previously provided by PSTN or ISDN access: carrying incoming and outgoing calls, telephone numbers and multiple simultaneous call channels between the hotel and the public telephone network.

Despite the name, it is not normally a physical trunk cable. It is a logical service carried across an internet connection, private circuit or managed voice network. One SIP trunk can support the hotel’s main number, DDI ranges for departments, outbound presentation numbers and an agreed number of concurrent calls.

For a hotel with a supported PBX, moving from ISDN to SIP can modernise the external connection without replacing every handset or internal extension. Numbers can normally be ported, subject to carrier validation and a managed cutover. The PBX continues handling reception groups, guestroom extensions, voicemail, wake-up calls and PMS integrations while the carrier-facing side becomes IP-based.

SIP trunk design needs more than a channel count. It should cover:

• Number inventory and porting: identify every main number, DDI, presentation number and service attached to the losing carrier before an order is placed.
• Concurrent calls: size capacity from actual busy-hour demand, reservation peaks, groups and expected growth rather than copying the old ISDN channel count blindly.
• PBX compatibility: confirm the software release, SIP licences, codec support, dial plan and any required session border controller or carrier interworking.
• Security: apply authenticated carrier connectivity, restricted signalling, fraud controls, strong administration and monitoring. A poorly protected voice platform can expose the hotel to toll fraud and service disruption.
• Call quality: check bandwidth, latency, jitter, packet loss, Quality of Service and contention across the hotel network and WAN.
• Resilience: decide how calls route if the PBX, SIP service, firewall, internet circuit or site power fails. Options may include secondary trunks, alternate carriers, diverse connectivity and automatic diversion to another property or mobile destination.
• Emergency calling: validate outbound caller identity, location information, dial rules and behaviour from reception, guestrooms and remote sites.

Our communications solutions cover SIP trunking as both a route to retain a suitable PBX and a foundation for new cloud, on-premises or hybrid telephony.

Cloud, on-premises or hybrid PBX with Alcatel-Lucent Enterprise

Connected Hospitality is an approved Alcatel-Lucent Enterprise Business Partner serving hospitality customers across the UK and Ireland. The strength of the ALE portfolio is that it does not force every property into the same model. It provides credible on-premises, hybrid and cloud routes, allowing the migration to reflect the hotel’s scale, existing estate, PMS requirements and resilience priorities.

OmniPCX Enterprise Purple for on-premises and hybrid estates. OXE Purple is designed for medium, large and complex environments. ALE documents support for SIP, IP, digital, analogue, DECT and IP-DECT connectivity, hospitality services, PMS integration, high availability and hybrid cloud connectivity with Rainbow. For a large hotel or resort with existing room phones, specialist endpoints and critical local calling, this breadth can make a controlled SIP migration more appropriate than an immediate move to a generic hosted system.

An OXE design can retain call control locally or within private infrastructure while using SIP trunks for public calls. Rainbow can then add mobile, desktop, messaging, presence and collaboration services. This creates a phased route: replace the obsolete carrier access now, preserve operationally useful hotel functions, and modernise endpoints or applications according to a defined lifecycle.

OXO Connect for smaller properties. OXO Connect provides a hybrid communications platform aimed at smaller and medium organisations, supporting analogue, digital, IP and SIP endpoints and trunks alongside Rainbow cloud services. It can be a strong fit where a smaller hotel needs local telephony and mixed endpoint support without the scale of an enterprise platform.

Rainbow Hub for full cloud PBX. Rainbow Hub combines cloud call control with unified communications and collaboration. ALE’s current Rainbow Hub product information describes a cloud PBX supporting telephony, call groups, routing, voicemail, operator services, applications and collaboration, connected to a chosen SIP service.

For hotels, Rainbow Hospitality adds the specialist operational layer. ALE describes integration between Rainbow Hub, OPERA Cloud or third-party PMS platforms, call accounting and room workflows. Functions include check-in and check-out events, room transfers, barring, wake-up calls and call records. The current solution also supports certified SIP endpoints and the reuse of suitable analogue phones through a certified analogue-to-SIP gateway.

Cloud can simplify management and connect staff across properties, but it transfers importance to the LAN, WAN, firewall, DNS, power and internet design. Our detailed cloud, on-premises and hybrid PBX guide explains why hospitality requirements should determine the architecture rather than a blanket preference for one deployment model.

What happens to analogue guestroom and back-of-house extensions?

The retirement of external PSTN services does not automatically require every analogue extension inside the hotel to be removed. A guestroom telephone connected to the hotel PBX is different from a telephone connected directly to a public analogue line. If a suitable PBX remains in service, its analogue extension cards may continue supporting internal handsets while the external trunks move from ISDN to SIP.

Where call control moves to an IP or cloud platform, an analogue-to-IP gateway can provide FXS extension ports for suitable analogue phones. The gateway generates the local line conditions the handset expects and converts its calls into SIP for the new platform. High-density gateways can preserve large numbers of guestroom phones and make use of existing copper pairs where the cabling is traced, tested and suitable.

This can avoid the cost and disruption of replacing hundreds of low-usage room handsets at once. It also creates a staged migration path: reception, reservations and management can adopt richer IP or cloud devices, while guestrooms remain analogue until refurbishment or commercial need justifies replacement.

The design still needs engineering. Confirm gateway port density, ring capacity, dialling behaviour, message-waiting method, emergency calling, fax or modem requirements, PMS workflows, cabinet space, network segmentation, power and UPS runtime. Existing cables must not be assumed to be correctly labelled or free from bridged connections simply because the old system worked.

Resilience changes when voice becomes IP

Traditional analogue lines could power a simple telephone from the exchange. IP telephony depends on local equipment and power: routers, firewalls, switches, PBX servers, gateways, handsets and internet access may all sit in the call path. That does not make IP voice inherently unreliable; it means resilience must be designed explicitly.

A hotel migration should identify which services must remain available during a power cut or connectivity failure. Reception calls may divert to another property or mobile team. Internal extensions may continue through a locally survivable PBX. Critical gateways may need UPS protection and an alternate WAN or cellular path. Call-routing changes should be automated and tested rather than dependent on an engineer making manual changes during an incident.

Connected Hospitality’s resilience services consider diverse connectivity, firewalls, switching and backup power as parts of one service chain. This is particularly important for a cloud PBX or centralised multi-property platform, where a local network failure can otherwise remove access to call control.

A practical PSTN migration plan for hotels

1. Build a complete service inventory. Collect invoices, numbers, circuit references and contracts from every provider. Walk the property and trace what connects to each line. Include dormant-looking sockets, remote buildings and services managed by contractors.
2. Classify each dependency. Separate PBX trunks, ordinary voice lines, broadband-bearing lines, lift communications, alarms, entry systems, fax, payment devices and telemetry. Record the service owner and operational impact of failure.
3. Audit the existing PBX and endpoints. Document platform, version, licences, support status, handsets, analogue cards, DECT, PMS interface, voicemail, call recording, dial plans and capacity. Decide what remains valuable and what is genuinely obsolete.
4. Choose the target architecture. Compare an OXE or OXO on-premises/hybrid route, Rainbow Hub cloud PBX and other suitable options against the property’s scale, analogue estate, integrations, support model and resilience needs.
5. Design the SIP and number migration. Validate number ownership, porting data, call capacity, carrier compatibility, emergency calling, inbound routing and failure diversions. Do not cease the losing service before successful porting and acceptance.
6. Engineer analogue retention. Decide which phones can remain on PBX ports, which can move through certified gateways and which should be replaced. Test the existing copper routes and document the new port mapping.
7. Give critical systems their own workstream. Agree lift and alarm changes with maintainers and monitoring centres. Record approvals, backup-power design, test scripts and acceptance evidence.
8. Prepare the network and power. Check voice VLANs, Quality of Service, firewall rules, SIP security, DHCP, DNS, PoE, UPS runtime and primary and backup connectivity. Our network and connectivity services address the infrastructure beneath modern telephony.
9. Pilot before the live cutover. Test departments, room phones, reception consoles, hunt groups, voicemail, PMS events, external numbers, emergency calls and failover. Schedule number porting and final cutover around hotel operations with a documented rollback route.
10. Remove only what has been proven redundant. Monitor billing after migration, cancel superseded lines deliberately and retain final records. An unexplained analogue charge may be waste—or it may be the only clue to a forgotten critical service.

Frequently asked questions

When is the UK PSTN switch-off?

BT plans to retire its PSTN by 31 January 2027. Other network operators may use different programmes. Hotels should confirm every service with its actual provider and complete migration early enough to test normal operation and failure scenarios.

Do we have to replace our hotel PBX?

Not necessarily. A supported SIP-capable PBX may continue using existing extensions and hotel integrations while its external ISDN access is replaced with SIP trunks. Replace, upgrade or retain the PBX according to supportability, requirements and total lifecycle cost—not solely because the PSTN is closing.

Can existing analogue hotel phones still be used?

Often, yes. They may remain on analogue ports of a suitable on-premises PBX or connect to a cloud or IP platform through a certified analogue-to-SIP gateway. Confirm handset features, line conditions, cabling, emergency behaviour, PMS functions, capacity and power resilience.

Will an analogue gateway keep a lift phone or alarm working?

It can be the correct solution for compatible equipment, but it is not guaranteed for every device. The exact lift phone or alarm protocol, gateway, carrier path, power backup and monitoring destination must be approved and tested end to end. Some systems should instead move to a purpose-built IP, cellular or dual-path product.

What is the difference between a SIP trunk and a cloud PBX?

A SIP trunk connects a PBX to the external telephone network over IP. The PBX can still be on the hotel’s premises. A cloud PBX hosts the call-control platform as a service away from the property. Cloud PBX services also use IP and SIP technologies, but the two terms describe different parts of the solution.