InfrastructureUK PSTN switch-off on 31 December 2025
The UK's copper phone network is going dark on December 31, 2025. If your building still has alarms, elevator phones, or SCADA systems dialing out over PSTN lines, you have got weeks to migrate them to IP or cellular—or they simply will not work anymore.
Verified for technical accuracy — Kodi C.
UK telecom operators will switch off the copper Public Switched Telephone Network (PSTN) on 31 December 2025. Openreach’s stop-sell program has already frozen new PSTN orders, and Ofcom is directing enterprises to migrate critical services to IP voice and data. Facilities, utilities, and manufacturing operators must revalidate alarms, lift phones, and SCADA dial-outs to prevent outages and comply with resilience duties.
Impact across infrastructure estates
- Industrial control and telemetry: Dial-up SCADA outstations, remote terminal units, and water telemetry that rely on analog PSTN lines will lose connectivity unless migrated to cellular, LPWAN, or IP VPN paths with equivalent failover.
- Life-safety systems: Fire panels, lift emergency phones, and intrusion alarms that signal over copper pairs need IP-capable communicators and dual-path supervision to stay compliant with BS EN 54 and insurer requirements.
- Voice and call routing: PBXs that depend on ISDN2e/30 circuits must shift to SIP trunks or hosted voice. Emergency calling needs power-resilient customer-premises equipment with battery backup to handle power cuts.
- Resilience assurance: Facilities using PSTN for out-of-band management or DR plans have to redesign runbooks so voice fallback and console access continue when primary WAN circuits fail.
Controls and metrics
| Control | Metric | Hook |
|---|---|---|
| Asset discovery | % of PSTN-dependent devices identified and recorded | ISO 27001 A.5 inventory; facilities CMDB |
| Migration readiness | Share of circuits with replacement design approved | Change advisory board sign-off; Ofcom migration guidance |
| Power resilience | Backup duration for VoIP gateways and modems (target >1 hour) | BS EN 54 fire-alarm signaling; business continuity plan RTOs |
| Dual-path signaling | % of alarms with IP + cellular supervision paths | Insurer security schedules; police URN compliance |
| Operational testing | Mean time to detect and resolve test call failures | Quarterly failover drills; service-level objectives |
Migration actions before December 2025
- Audit every endpoint: catalog fax lines, lift phones, telemetry modems, and PBXs still using PSTN/ISDN. Map each to a replacement circuit and owner.
- Design IP replacements with failover: Use SIP trunks with geographic redundancy, LTE/5G or satellite backup for alarms, and QoS policies across LAN/WAN. Validate jitter and packet-loss budgets for voice MOS targets.
- Stabilize power: Add UPS coverage for optical network terminals, routers, and ATA devices in plant rooms and comms closets so emergency calling remains available during power cuts.
- Retest safety cases: Run integrated tests with alarm receiving centers and elevator maintenance providers to prove supervised signaling meets BS EN 50136 and EN 81 call-routing rules.
- Update contact and DR plans: Refresh incident response runbooks, vendor call trees, and out-of-band access procedures to reflect IP-based recovery paths.
Timeline
- Now–Q2 2025: Finish discovery and design approvals; order replacement circuits and hardware while supply chains remain unconstrained.
- Q3 2025: Execute migrations region by region; complete failover drills with power-cut simulations.
- Q4 2025: Freeze changes and monitor for latent PSTN dependencies before the 31 December switch-off; keep analog-to-IP adaptors on hand for emergency remediation.
Bottom line: The PSTN sunset is a fixed 2025 deadline. Infrastructure leaders should remove copper dependencies now, layer battery-backed IP voice, and rehearse failover so life-safety systems, telemetry, and support lines stay online when the switch-off arrives.
Supply-chain and vendor governance
Migration requires new routers, optical network terminals, and SIP-capable PBXs; lead times can stretch when multiple operators compress orders before the 2025 cutover. Work with approved suppliers early, and document alternatives for devices that must meet BS EN 50136 alarm signaling or EN 81 lift communication standards. Check that maintenance vendors are certified on the replacement hardware and that service-level agreements include battery replacement and firmware patching cadence.
Contracts with alarm receiving centers (ARCs) and telecom carriers should include explicit acceptance criteria for packet loss, jitter, and registration failover during outages. Require ARCs to support encrypted signaling paths (for example, TLS or IPsec) and dual data centers so life-safety alerts continue if a single site is offline.
Change management and assurance
- Run book validation: Update diagrams and operational handbooks to reflect SIP trunks, media gateways, and LTE backup paths. Attach schematics to CMDB entries and verify that technicians can reach powered network closets during building evacuations.
- Testing cadence: Institute monthly automated test calls for alarms and elevators, logging mean time to detect anomalies and escalation paths to carriers. Trend failure causes to address cabling, configuration, or power gaps before the deadline.
- User communication: Brief occupants and helpedesk teams on how emergency calling works after migration, including expectations during mains failures. Provide battery backup status indicators in equipment rooms.
These measures create an audit trail for insurers and regulators demonstrating that copper removal did not degrade safety outcomes.
Risk scenarios to rehearse
- Extended power failure: Simulate multi-hour outages to verify battery-backed ONTs, switches, and routers keep elevator and alarm calling alive for the duration required by business continuity plans.
- Carrier outage during migration: Practice fallbacks where SIP trunks fail mid-cutover, ensuring cellular gateways or secondary carriers pick up traffic without manual intervention.
- Legacy device discovery: Run last-mile sweeps for undocumented modems in manufacturing or utilities sites that may have been missed during initial inventory.
Ofcom regulatory requirements and vulnerable users
Ofcom's General Conditions require communications providers to protect vulnerable customers during the PSTN migration. Providers must identify customers who depend on landlines for telecare, medical alert devices, or accessibility equipment and ensure equivalent IP-based services maintain reliability during power outages. The Communications Act 2003 obligations on access to emergency services apply equally to VoIP, meaning battery backup or alternative calling methods must be in place.
For enterprises operating premises with vulnerable occupants—care homes, sheltered housing, hospitals—migration planning must show continuity of protected services. Document how replacement systems meet Ofcom's resilience guidance, including one-hour minimum battery backup for voice services and automatic failover to cellular where premises lack generator backup.
BT Wholesale and alternative carrier considerations
While Openreach manages the physical copper network, voice services route through BT Wholesale or alternative carriers. Migration involves both the access layer (copper to fiber/cellular) and the service layer (PSTN trunks to SIP). Enterprises with multi-site estates should consolidate SIP trunk procurement to simplify management and negotiate volume pricing, while maintaining carrier diversity for resilience.
Alternative carriers like Virgin Media Business, TalkTalk Business, and Gamma offer SIP services that may provide better coverage or pricing in specific regions. Evaluate carrier SLAs for call completion rates, mean time to repair, and geographic redundancy of their VoIP platforms before committing to migration contracts.
Funding and prioritization
Plan capital spend across 2024–2025 to replace PSTN-dependent assets in high-risk locations first—such as hospitals, elevators serving critical infrastructure, and water treatment telemetry—so limited engineering time targets the most consequential circuits. Track spend against resilience KPIs and make procurement status visible to executives to prevent budget raids.
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Coverage intelligence
- Published
- Coverage pillar
- Infrastructure
- Source credibility
- 93/100 — high confidence
- Topics
- Telecom resilience · PSTN withdrawal · Voice over IP · Critical infrastructure monitoring
- Sources cited
- 3 sources (openreach.co.uk, ofcom.org.uk, iso.org)
- Reading time
- 6 min
Cited sources
- Openreach: The withdrawal of the UK Public Switched Telephone Network — openreach.co.uk
- Ofcom: Preparing for the withdrawal of the PSTN — ofcom.org.uk
- ISO/IEC 27017:2015 — Cloud Service Security Controls — International Organization for Standardization
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