The UK’s legacy Public Switched Telephone Network (PSTN) is being retired. According to the latest UK Government connectivity timeline, all users of the Openreach PSTN must migrate to replacement services by 31 January 2027.
This affects more than traditional desk phones. Businesses must assess ISDN, analogue lines, copper broadband, alarms, payment terminals, lift phones, intercoms, access systems and other connected equipment before migration.
Free IT, telecoms and cybersecurity review — we'll audit your lines, devices and network, and tell you exactly what needs changing before 31 January 2027. Call 0330 174 9142 to arrange a free review, on site, by phone or on Teams.
What is the UK PSTN switch-off?
The UK PSTN switch-off is the retirement of the analogue telephone network and associated legacy copper services. Traditional phone calls will move to internet-based digital voice technologies, including Voice over Internet Protocol (VoIP), hosted telephony, SIP trunks and cloud phone systems.
The Department for Science, Innovation and Technology guidance confirms that PSTN-reliant devices will require upgrading to digital technologies. The same guidance identifies analogue phones, alarms, payment terminals, lifts, intercom systems and broadband services as potentially affected.
This is a planned infrastructure modernisation rather than a routine telephone upgrade. Businesses that delay may face service failure, unsupported equipment, emergency communication risks and avoidable operational disruption.
Why must businesses act before 31 January 2027?
Businesses must act before the deadline because legacy services will not continue indefinitely after the Openreach transition. The latest official timeline states that all Openreach PSTN users need to be migrated by 31 January 2027.
The need for preparation is reinforced by network reliability concerns. GOV.UK reports that PSTN incidents increased by 45% in 2024, with more than 2,600 major incidents recorded during 2024/25. Digital services provide a more modern platform, but the migration still requires structured planning, device compatibility checks and resilience testing.
Key takeaways
- PSTN and many ISDN services are being retired.
- Digital voice, business VoIP and SIP-based services are the principal replacements.
- ADSL and some FTTC services may also require migration.
- Alarms, lifts, payment terminals and access systems require separate checks.
- Digital voice depends on local power and network availability.
- The migration should be audited, tested, documented and completed before the deadline.
What are the 10 steps businesses must take?
Businesses should treat the PSTN switch-off as a telecoms, infrastructure and business continuity project. The following ten steps provide a practical migration framework.
1. Audit every telephone line and connected device
Start with a full site audit across offices, warehouses, retail premises, workshops, outbuildings and remote locations. Review telecoms bills, maintenance contracts, network diagrams and supplier records.
Identify:
- Analogue telephone lines
- ISDN2 and ISDN30 services
- ADSL and FTTC broadband
- Fax machines and franking machines
- Fire and intruder alarms
- Lift emergency phones
- Payment terminals and EPOS systems
- Door-entry and intercom systems
- CCTV diallers and monitoring equipment
- Building management systems
- Backup lines and failover connections
Do not rely solely on IT records. Many PSTN-connected devices are managed by facilities, security, property or finance teams.
2. Identify all ISDN and legacy phone-system dependencies
ISDN phone systems may support hunt groups, direct dial numbers, call forwarding, voicemail, conference facilities and contact-centre functions. Record the current configuration before considering replacement options.
A suitable replacement may include hosted VoIP, SIP trunking, a cloud PBX or an upgraded on-premise telephone system. The correct architecture depends on handset numbers, call volumes, remote working requirements, call recording, CRM integration and business continuity objectives.
Helping Hand Technology Services can support businesses with telephone systems and telecoms services, including on-premise and cloud-based communication environments.
3. Confirm broadband and fibre readiness
Digital voice relies on a suitable IP connection. Businesses should confirm whether existing broadband has sufficient capacity, stable latency and appropriate upload performance for voice traffic and other critical applications.
Review whether the site can support:
- Full Fibre or FTTP
- Business-grade broadband
- Leased-line connectivity
- Separate voice and data services
- Dual-WAN or 4G/5G failover
- Quality of Service (QoS) configuration
- Managed firewall and router equipment
The GOV.UK guidance for PSTN and ISDN preparation highlights that fibre connections do not carry power in the same way as copper lines. Businesses must therefore plan for local power loss as part of the migration.
4. Select the right digital voice or business VoIP platform
Digital voice is not a single product. Businesses can choose from hosted VoIP, cloud PBX, SIP trunks, Microsoft Teams telephony integrations and other IP-based platforms.
Selection should be based on operational requirements, not headline features. Assess:
- Number portability
- Call quality and capacity
- Mobile and remote-user support
- Auto-attendant and call queues
- Call recording and reporting
- CRM and Microsoft 365 integration
- Emergency calling arrangements
- Supplier support and service levels
- Data protection and security controls
- Exit and continuity arrangements
A structured design protects existing numbers, call flows and customer contact channels while creating a more scalable communications platform.
5. Protect business numbers and call routing
Telephone numbers are operational assets. Before migration, document every main number, direct dial number, hunt group, voicemail route, emergency contact and out-of-hours message.
Confirm:
- Which numbers must be retained
- Which numbers are no longer required
- Where calls should route during migration
- How temporary forwarding will operate
- How emergency calling information will be maintained
- How reception and contact-centre workflows will change
Number porting should be scheduled carefully, with a controlled change window and rollback plan where available.
6. Upgrade and test alarms
Alarm systems are among the highest-risk PSTN dependencies. Fire alarms, intruder alarms and monitoring systems may use analogue signalling to communicate with a control centre.
Contact the alarm maintainer and monitoring provider to confirm whether the system supports IP, 4G, 5G or dual-path signalling. Replacement solutions should be assessed against monitoring requirements, insurance conditions, battery life and site coverage.
Do not assume that connecting an alarm to a router’s analogue terminal adapter will provide an equivalent solution. The Department for Education’s technical guidance notes that ATA ports are designed for voice calls and are not suitable for alarms or other machine-to-machine services.
Free IT, telecoms and cybersecurity review — we'll audit your lines, devices and network, and tell you exactly what needs changing before 31 January 2027. Call 0330 174 9142 to arrange a free review, on site, by phone or on Teams.
7. Check payment terminals, lift phones and access systems
Payment terminals that dial over analogue lines may fail after migration. Businesses should contact their merchant services provider and arrange IP-connected or mobile-enabled equipment.
Lift emergency phones require separate attention. Engage the lift maintenance provider to confirm that the emergency autodialler will operate over the replacement connection and during a power cut.
Also review:
- Door-entry intercoms
- Car park barriers
- CCTV diallers
- Vending machines
- Franking machines
- Specialist monitoring systems
- Building management and environmental controls
8. Secure the new IP communications environment
Moving from copper services to IP-based communications introduces a greater dependency on business networks, routers, firewalls, user accounts and cloud platforms.
Businesses should protect digital voice with:
- Segmented voice networks or VLANs
- Strong administrator authentication
- Firmware and patch management
- Secure SIP and platform configuration
- Access logging and monitoring
- Supplier security reviews
- Tested backup and recovery procedures
- Documented incident response processes
Helping Hand Technology Services provides cybersecurity support for business systems and connected infrastructure. This should be considered alongside telecoms migration, particularly where voice, access control, CCTV and building systems share the same network.
9. Implement backup power and connectivity resilience
Digital voice, broadband routers, switches and wireless equipment require electrical power. A mains failure can therefore interrupt voice services unless suitable resilience is installed.
Businesses should assess:
- Uninterruptible Power Supplies (UPS)
- Router and switch backup power
- Generator requirements
- 4G or 5G failover
- Dual-provider connectivity
- Battery-backed alarms and lift phones
- Emergency contact procedures
- Staff access to mobile communications
Providers must support emergency-call continuity in relevant circumstances, but this does not automatically provide full business continuity. Critical operations may require a properly engineered UPS, generator or dual-path design.
10. Test, document and schedule the migration
The final step is controlled implementation. Do not treat the provider’s service activation date as the end of the project.
Complete and record:
- Inbound and outbound call testing
- Number presentation checks
- Call queue and voicemail testing
- Alarm signalling tests
- Lift emergency-call tests
- Payment terminal authorisation tests
- Door-entry and intercom tests
- Power-failure simulations
- Failover connectivity tests
- Staff training and escalation procedures
Maintain an asset register showing each service, supplier, replacement technology, test date, owner and support contact. Businesses should also schedule migration with sufficient time to resolve compatibility issues before 31 January 2027.
For related infrastructure planning, see our guidance on structured cabling for UK businesses.
Is digital voice the same as VoIP?
Yes, in practical terms, digital voice uses VoIP technology to carry calls over an IP network rather than an analogue copper telephone line. The service may be delivered as hosted VoIP, SIP trunking, a cloud PBX or a provider-branded digital voice product.
The important distinction is that not every PSTN-connected device can use a standard VoIP handset or router adapter. Alarms, lift phones and machine-to-machine systems require compatible solutions designed and tested for their specific function.
Does the PSTN switch-off affect broadband?
Yes. Businesses using ADSL or copper-dependent FTTC services should confirm their migration position with the connectivity provider. The replacement may be full fibre, a leased line, fixed wireless access, satellite backup or another PSTN-independent service.
Connectivity should be sized for voice, cloud applications, remote access, security systems and normal business traffic. A faster connection alone does not guarantee resilience or call quality; routing, firewall configuration and network management also matter.
What should businesses do now?
Businesses should begin with a documented audit and engage their telecoms, alarm, lift, payment and building-system providers. Helping Hand Technology Services can assess the current environment, define a suitable digital voice and connectivity architecture, coordinate technical dependencies and support structured testing.
Free IT, telecoms and cybersecurity review — we'll audit your lines, devices and network, and tell you exactly what needs changing before 31 January 2027. Call 0330 174 9142 to arrange a free review, on site, by phone or on Teams.
Frequently asked questions
When is the UK PSTN switch-off?
The Openreach PSTN migration must be completed by 31 January 2027, according to the official UK telecommunications connectivity timeline.
What replaces PSTN?
Common replacements include digital voice, business VoIP, hosted PBX, SIP trunks, full-fibre broadband and other IP-based telecoms services.
Will an existing phone handset continue to work?
It may continue to work through a compatible provider-supplied adapter or digital voice service. However, the business must confirm compatibility with the communications provider and check whether other devices share the same line.
Will alarms and lift phones stop working?
PSTN-dependent alarms and lift phones may stop communicating when the legacy service is withdrawn. They require assessment and, where necessary, migration to IP, cellular or dual-path equipment with suitable backup power.
Does a router’s ATA port support an alarm?
No. ATA ports are generally intended for voice calls. They should not be treated as a suitable replacement for alarm or machine-to-machine connectivity without confirmation from the equipment manufacturer and monitoring provider.
What is the first action a business should take?
Complete a site-wide audit of all analogue lines, ISDN services, copper broadband and connected devices. Record the supplier, purpose, location, replacement requirement and business owner for every service.
How can Helping Hand Technology Services assist?
Helping Hand Technology Services provides telecoms guidance, telephone-system support, network infrastructure, connectivity planning and cybersecurity services to help businesses migrate in a controlled and documented manner.