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The PSTN challenge

Challenge update Autumn 2021: After a number of proposals from suppliers on mitigating the changes needed for PSTN equipment the internal costs for installation of these outweighed the benefits provided by the solutions.  Instead we have opted for like-for-like replacement using existing power infrastructure.

In May 2018 OpenReach (BT) launched a consultation on the move from analogue telephony to digital voice services by 2025.

We have ~2800 sites that rely on analogue PSTN (Public Switched Telephone network) services to communicate back to our central control systems.

We need to replace these lines to maintain visibility and control of the Wessex Water estate.


PSTN has existed in this country since the 1800s. The technology continues to serve us well, connecting ~2800 telemetry sites to our central alarm systems and the control room.

This technology is being withdrawn by 2025 when telemetry will cease to work. In addition, substantial interim changes during 2023 may affect our telemetry services.

To tackle this challenge, we have created a cross departmental team to explore solutions for the removal of traditional voice services, enabling the mitigation of the risks and establishment of a road map.

By opening up the challenge for market engagement rather than specifying the solution we require, we are exploring a range of existing, new and future solutions from a much wider field of suppliers.

The aim is to identify and deliver the best value solution to our future site communication needs.

Our approach

While we realise a tactical solution is required to manage the risk and ensure we continue to operate after 2023-2025, we also need to incorporate this tactical approach within a strategic plan.

So we are engaging with the market to inform and develop our strategy. Our business will need to change ~2800 sites to alternative communication and data collection/aggregation technologies.

These alternatives can provide access to new capabilities to meet our future regulatory objectives. The strategic plan will ensure risks are managed and capabilities such as cloud computing and analytics are used where the added value can be quantified.

To achieve this a strategic proposal document was developed and shared with Gartner to advise on market maturity and global experience in this issue.

To provide as open approach as possible we chose to initially engage suppliers through the Achilles platform, where we shared our proposal. The proposal had several open questions about our challenge which required a form of response from the vendors.

The cross departmental team then reviewed the proposals and selected a variety of vendors with different approaches to our challenge. These vendors have been invited to market engagement meetings to present their high-level approaches.

No company which responded has been discounted from the ongoing process, even if they were not selected for the initial market engagement suggestions, with a view to reengaging with them as we develop our approach.

Next steps

The market engagement has allowed vendors to influence and steer our strategy to the PSTN challenge. We are now moving to the next stage of our strategy where we will release a more detailed specification document covering our end-to-end approach to the challenge, and incorporating the input from the vendors.

Vendors who responded to the Achilles submission will be invited to comment on the more detailed document and to highlight areas for improvement or challenge.

We will then move to the next stage which will be a procurement exercise, possibly incorporating some proof of concept trials. We’ll share our progress in the blog section of this site.

If you’d like more information please email [email protected] .