legacy telephone system



For operational, technical and commercial reasons, digital telephone systems (PABX systems) based on designs from the early 1980s are now becoming ‘end of life’.

While these systems, e.g. Siemens ISDX, MXOne, Avaya Definity, Avaya (exNortel) Meridian and Mitel SX2000 etc., are probably technically capable of providing reliable albeit basic telephony services for at least another 10 years, circumstances will dictate that they need to be withdrawn from service over the next few years.

Consequently, all organisations still relying on a digital PABX system should have a strategy for replacing it with either a new product or service (or a combination) by mid-2018 at the latest.

The objectives of this paper are to provide an insight to the risks of continuing to rely on an obsolescent digital PABX system and suggestions on how to move forward to secure the future of telephony within an organisation.


Despite providing reliable telephony service to thousands of public and private sector organisations in the UK, digital PABX designs are based on hardware and software that in some cases is now over 30 years old.

As such, manufacturers are experiencing difficulties with the sourcing of new hardware components and the retention of software engineers with the requisite programming skills. In addition, they are under constant pressure to develop new products and cut operational costs to remain competitive.

Consequently, we are now starting to see the following trends in the PABX marketplace as manufacturers increasingly focus on their new products:

  • No further sales of new systems
  • No new software releases to provide new features
  • on existing systems
  • No new licence sales to expand existing systems
  • No availability of new parts to expand existing systems
  • An inability to integrate existing hardware into
  • new solutions from the same manufacturer
  • Declining stocks of critical second hand parts
  • for maintenance, e.g. power units, processors,
  • operator consoles etc.


By continuing to rely on obsolescent PABX systems, organisations will be taking on one or more of the following risks:

  • The inability to support user requirements for hot desking,
  • mobility and home working
  • The inability to extend service to new locations due
  • to lack of equipment
  • Rising maintenance costs as maintainers struggle
  • to support old equipment
  • Elongated response times as the number
  • of maintenance engineers reduces due to employee churn,
  • redundancies and retirement
  • Long periods of system down-time as maintainers struggle to locate
  • and deliver critical second hand parts to site to resolve faults

Even at this mid-point stage of the digital PABX decline, we have seen some of our clients suffer from 24 hour system outages, outrageously expensive maintenance contracts and fragmented telephony infrastructures that become overly complex and deliver poor customer service.


To address the challenges and risks as PABX systems get older and manufacturers and maintainers increasingly focus on newer products, organisations need to develop and implement strategies to retire their digital PABX systems in a timely and organised manner.

With replacement solutions requiring significant capital investment and procurements often taking in excess of 12 months to complete, it can easily take at least 3 years to plan, fund and execute the transition from a large digital PABX system.

With those timescales, organisations planning to develop their strategy in the 2017/18 financial year may not actually complete their telephony project until 2020/21.

Do you know how much it will cost to replace your PABX system?

How much notice will your Finance Director need to find the required capital?

What are my options?

Until recently, most organisations simply replaced their old telephone system with a new telephone system on a like for like basis. Over the last 30 years, the two main technology trends have been electro-mechanical to digital and digital to IP.

However, today’s marketplace is more complex with IP telephony systems, Unified Communication solutions (UC), managed IP telephony services, hosted IP telephony services and mobile only solutions on offer from a myriad of suppliers.

What’s right for your organisation, a product or a service?

Will you connect all users to the same system / service on a ‘one size fits all’ basis?

Alternatively, will you ‘mix and match’ products and services from different suppliers to meet specific requirements in the most cost effective manner?

What factors will you take into account? Capital? Revenue? Feature sets? Ease of management?

Who will take the decisions? ‘Business Leads’, IT or Finance?


There will inevitably be a last minute rush for new systems and services in 2018/19 which will lead to rising prices and an increasing demand for engineering resources.

Astute ICT Managers should be developing their strategies now to realise better value and deliver successful projects to the business.

Can you afford to delay developing your strategy?

Are you willing to pay more for your solution as the marketplace gets busier?


In simple terms:

  1. Identify the user requirement for communicating. While in the past this was
  2. limited to simply calculating the need for fixed desk phones, today you need
  3. to consider the use of softphones, cordless extensions, mobile smartphones
  4. and tablets. You also need to consider integrating your telephony solution
  5. with other forms of communicating such as instant messaging, email, video
  6. conferencing, web conferencing and social media. Would your customers prefer to use Skype and Facebook to contact you?
  7. Confirm the organisation’s position on finance, outsourcing
  8. and contract terms etc.
  9. Identity and discuss the options for meeting the user requirements.
  10. These include purchasing a system, subscribing to a service or combination
  11. of both. This task should include consideration of technical, operational
  12. and financial issues.
  13. Decide on the most appropriate option for the organisation.
  14. Build the business case setting out what is going to be provided,
  15. how much it’s going to cost and the benefits it will deliver.
  16. Procure the requisite products and services.
  17. Implement and transition to the new arrangements. Do you have the time to undertake this work? Do you have the relevant skills, knowledge and experience in-house to undertake this work? Would you like to benefit from other projects in your sector?


4C Strategies is an independent ICT consultancy with an 18 year track record in major telephony projects.

We’ve helped numerous NHS Trusts, Universities, Colleges, Councils and private sector companies to replace large mission critical telephony infrastructures with new systems and services.

Working with small district councils to large acute NHS Trusts with Accident & Emergency departments, our experience covers PBX systems, IP Telephony, Unified Communications, hosted telephony, data networking and video conferencing.

Our services include:

  • Identifying business requirements
  • Developing technology strategies
  • Building business cases
  • Preparing procurement documentation
  • Managing procurements
  • Preparing contracts
  • Managing implementations
  • Realising benefits


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