How to Prepare for the BT Switch Off 

In December 2025, the BT Switch Off will mark the end of the Public Switched Telephone Network (PSTN) and Integrated Services Digital Network (ISDN) services in the UK, transitioning all phone lines to a digital network using Internet Protocol (IP) over a fibre-based service. This significant shift affects not just voice services but also potentially broadband, signalling a move towards more modern, efficient communication technologies. As we transition to this digital era, understanding the BT Switch Off’s implications is crucial for businesses and individuals alike.

The switch from PSTN and ISDN to an IP-based network necessitates exploring alternatives, such as VOIP phone systems for businesses, to ensure seamless communication continuity. This article will delve into the timeline and phases of the BT Switch Off, its impact on businesses, and the benefits of embracing VOIP technology. We aim to guide you through preparing for the transition, ensuring your communication infrastructure does not just survive but thrives in the post-BT Switch Off landscape.

Understanding ISDN and PSTN

ISDN: Integrated Services Digital Network

ISDN, which emerged around 1960 due to the limitations of the analogue system for long-distance connections, represents a set of communication standards for simultaneous digital transmission of voice, video, data, and other network services over the traditional circuits of the public switched telephone network. It allows for multiple digital channels to be operated simultaneously through the same regular telephone line, providing higher data rates and better quality. ISDN is split into two key types:

  1. Basic Rate Interface (BRI): Typically used in home and small business environments.

  2. Primary Rate Interface (PRI): Suitable for larger setups with greater data and voice transmission needs.

PSTN: Public Switched Telephone Network

Contrastingly, PSTN is the traditional analogue phone system reliant on copper wires to transmit voice communications. The technology underpinning PSTN has been the backbone of voice communication for over a century, offering only basic data functionalities with significant limitations in speed and quality. It operates on a single channel, making it less flexible compared to ISDN.

Comparative Overview

  • Transmission Protocol: Digital for ISDN vs. Analogue for PSTN.
  • Data Transfer Rates: Up to 128 Kbps for ISDN, compared to PSTN’s 56 Kbps.
  • Call Setup Time: Significantly quicker on ISDN.
  • Signal Quality: Higher in ISDN.
  • Number of Channels: Up to 30 in Europe and 23 in the US for ISDN, only 1 for PSTN.
  • Simultaneous Connections: Multiple for ISDN, one for PSTN.
  • Cost: Generally higher for ISDN due to increased capabilities.

These distinctions underscore why ISDN has been preferred by larger businesses requiring robust, multi-channel communication solutions and why the shift to more advanced technologies like VoIP is necessary as the capabilities of PSTN and ISDN no longer meet modern communication demands.

The Timeline and Phases of The Switch-Off

Phased Rollout and Key Dates

  1. Initial Phase – Stop Selling ISDN and PSTN Lines: As of September 2023, BT Openreach will halt the sale of traditional phone lines across all exchange areas. This includes both new activations and modifications to existing analogue and ISDN lines.

  2. City-by-City Stop-Sell Implementation: Between December 2020 and August 2023, Openreach is implementing a phased stop-sell approach. Each city reaches its specific deadline, after which no new analogue or ISDN lines can be purchased, nor can existing services be altered.

  3. Final Phase – Complete Switch-Off: By the end of 2025, the entire network of PSTN and ISDN services will be decommissioned. This will make room for the more modern VoIP systems that are set to replace the legacy networks.

Transition to VoIP Technology

  • Preparation for Businesses: Organisations are urged to consider upgrading to internet-based solutions well before the 2025 deadline to ensure uninterrupted service. This involves transitioning from traditional telephony to VoIP (Voice over Internet Protocol) systems.

  • Migration Deadline: All existing ISDN/PSTN channels must be migrated by the year 2025. Failure to do so will result in the loss of telephony services, as these older networks will no longer be operational.

  • Ongoing Upgrades and Support: Openreach has been actively rolling out the full fibre network (FTTP) across the UK to support the new digital infrastructure, ensuring that businesses and consumers experience a seamless transition.

Considerations and Planning

  • Impact on Existing Equipment: The switch-off will not immediately affect existing equipment; however, businesses are encouraged to act sooner rather than later to upgrade their systems to compatible technologies.

  • Variable Timeline: While the goal is to complete the switch-off by 2025, timelines may vary, with some areas potentially transitioning earlier or later than others. Businesses should stay informed about the specific timelines affecting their locations to plan accordingly.

Impact on Businesses

The BT Switch Off represents a significant shift for businesses, impacting operations depending on their reliance on PSTN and ISDN services. As we move towards Internet-based communication solutions, the landscape of corporate connectivity is set to change dramatically.

Advantages of Transitioning to VoIP Systems

  1. Enhanced Connectivity and Quality: VoIP technology uses internet connections to transfer voice data, which enhances call quality and reliability.

  2. Cost-effectiveness and Scalability: These systems are not only more affordable but also scale with the growth of the company, making them ideal for expanding businesses.

  3. Support for Modern Work Environments: VoIP systems facilitate remote working with features like video conferencing and mobile integration, thus fostering better customer relationships and flexible work arrangements.

Necessary Upgrades and Considerations

  • Equipment Updates: Transitioning to digital means updating essential systems such as door entry, alarms, and emergency communication devices in lifts.

  • Training and Hardware Acquisition: Businesses will need to invest in new hardware suited for VoIP and train their staff to handle the new technology effectively.

Planning for a Smooth Transition

  • Early Adoption: To avoid last-minute hassles and potential service disruptions, businesses are advised to start their transition well before the final switch-off deadline.

  • Customisation of Services: Choosing the right VoIP features—like caller ID, call forwarding, and digital faxing—will be crucial to meet specific business needs.

  • Consultation and Implementation: Engaging with knowledgeable VoIP providers for efficient implementation and ongoing support will ensure businesses maintain continuity and leverage new capabilities to their fullest.

By proactively adjusting to these changes, businesses can ensure a seamless transition while optimising their communication infrastructure for the future.

Exploring the Alternatives

VoIP and SIP: The Future of Business Telecommunications

As businesses face the impending BT Switch Off, exploring robust alternatives like VoIP (Voice over Internet Protocol) and SIP (Session Initiation Protocol) becomes imperative. VoIP transforms voice signals into data packets transmitted over the internet, eliminating the need for traditional phone lines. This technology not only enhances call quality but also reduces costs and scales with business growth. SIP, on the other hand, allows businesses to keep their existing phone systems while connecting to the internet for voice communications, maintaining current features and call quality.

Key Benefits and Implementation Strategies

  1. Cost-Effectiveness and Scalability: Both VoIP and SIP offer significant cost savings compared to traditional ISDN lines. They allow for easy scaling, making them ideal for businesses anticipating growth.

  2. Enhanced Features: These technologies support advanced features like call forwarding, virtual meetings, and integration with collaboration tools, which are essential for modern business operations.

  3. Flexibility in Communication: With options like mobile VoIP and unified communications, businesses can ensure connectivity across various devices and platforms, enhancing overall productivity and collaboration.

Transitioning to IP-Based Solutions

Transitioning to IP-based solutions involves several considerations to ensure a smooth changeover. Businesses should assess their current infrastructure to determine compatibility with VoIP or SIP technologies. For those with existing PBX systems, SIP Trunking can seamlessly integrate into these environments, providing a bridge to newer technologies without a complete overhaul. Additionally, engaging with experienced suppliers who can deliver tailored SIP channels or connect to cloud services like Microsoft Teams can facilitate a more efficient transition process.

Preparing for the Transition

As businesses anticipate the upcoming BT Switch Off, preparing for the transition to IP-based solutions such as VoIP is essential. Here are the initial steps to ensure a smooth changeover:

Step 1: Review and Identify Connected Hardware

Start by auditing all hardware and functions that rely on your current phone lines. This includes checking if your systems are compatible with VoIP technology or if you require new installations. It’s crucial to identify every component—from fax machines to security systems—that will be affected by the switch to ensure nothing is overlooked.

Step 2: Create a Transition Roadmap

Developing a detailed plan is vital for a seamless transition. This roadmap should include:

  1. Timeline for Transition: Aim to start preparations by 2024 to mitigate last-minute hurdles and potential extra costs.

  2. Infrastructure Assessment: Evaluate your current internet connectivity to ensure it can support high-quality VoIP communications.

  3. Provider Comparison: Utilise tools like our free quote comparison to choose the best VoIP provider that fits your business needs.

  4. Training and Updates: Plan for staff training on the new systems and keep everyone informed about the transition stages.

Step 3: Implement the Change

Once your plan is in place, begin the implementation phase. This might include:

  • Switching to VoIP: Assess whether your existing phone systems can be adapted using an adaptor device, or if a new system is required.

  • Porting Phone Numbers: Ensure you have a strategy to port your existing numbers to the new IP system to maintain business continuity.

  • Testing and Adjusting: After installation, thoroughly test the new system to iron out any issues and make necessary adjustments.

By following these steps, businesses can not only ensure a smooth transition but also take advantage of the enhanced capabilities and cost savings associated with modern IP telephony solutions.

Our Thoughts & Next Steps

As we navigate towards the 2025 BT Switch Off, understanding and preparing for the transition from traditional PSTN and ISDN lines to innovative IP-based solutions is more critical than ever for businesses. This shift is not just a mandatory upgrade; it represents a significant improvement in how businesses communicate, offering enhanced call quality, scalability, and cost-effectiveness. By embracing VoIP technology, businesses stand to benefit from a modernised communication system that supports the dynamic needs of today’s work environments and fosters seamless remote work capabilities, thereby future-proofing their operations.

Ensuring a smooth transition requires early planning, understanding the impact on current infrastructure, and identifying the right VoIP solutions that meet specific business needs. View our VoIP solutions for a comprehensive guide on making this transition as efficient and beneficial as possible. The culmination of efforts to migrate to a digital network underscores a broader move towards embracing digital transformation, paving the way for more innovative, flexible, and efficient ways of conducting business. As we look towards this digital horizon, the importance of staying ahead in technology adoption has never been clearer, marking a pivotal moment for businesses to evolve and thrive in the digital age.


1. How should businesses prepare for the PSTN switch-off?
To prepare for the PSTN switch-off, businesses must transition to all-IP services. This change is necessary to maintain the ability to make and receive phone calls and access the internet. It may involve upgrading phone systems and other related equipment, and potentially changing phone numbers.

2. What are the implications of BT’s switch-off?
The switch-off by BT will impact more than just voice services; it will also necessitate upgrades to broadband services. Devices that currently rely on the PSTN network, such as alarms, EPOS machines, door entry systems, CCTV systems, and faxes, will cease to function. Additionally, the Integrated Services Digital Network (ISDN) will also be discontinued.

3. What does the ISDN switch-off entail?
The ISDN switch-off involves the phasing out of ISDN technology by telecommunications companies. This is being done in favour of adopting newer, broadband internet-powered technologies that offer more advanced capabilities.

4. Will I need to replace my phone after the PSTN is switched off?
Post-PSTN switch-off, your existing telecom devices will still be physically operational but will not have any service connection. This means that while the devices can turn on and function, they will not be able to perform tasks involving service connectivity like making calls or sending faxes.