Moving on from legacy PBX / ISDN

Despite unprecedented levels of transformation in business technology, one area of an organization is often found to be still using outdated, legacy infrastructure: the office telephone system.

Although the telecommunications industry’s average equipment lifecycle is five to seven years, during the economic downturn many organizations have preferred to stick with their existing systems, operating an ‘if it ain’t broke, don’t fix it’ mentality. Continuing to rely on aging Private Branch Exchanges (PBX) many businesses find themselves stuck with antiquated ISDN voice and data integration and reliant on the Publicly Switched Telephone Network (PSTN).

Issues with legacy PBX and ISDN systems

Unfortunately, although these telecoms assets have often served a business well for many years retaining them can pose a number of important issues, some of which are rapidly becoming critical. Even if a system meets current operational needs, it is unlikely to continue to do so in a changing environment.

As PBX equipment ages, operational costs rise and failures become prohibitively disruptive, particularly as vendor service agreements come to end, and spare parts and expertise become scarce. Older systems can also be insecure and are particularly susceptible to PBX/dial-through fraud in which hackers target private switches to make high volumes of premium rate or overseas calls.

A particular pressure facing many PBX owners in the next few years will be the phasing out of BT’s ISDN service, and equipment that is reliant on this will have to be retired from service. Although ISDN has performed well over the years in terms of business-grade voice quality and sub-broadband data speeds, it can be costly and lacks flexibility (for example, having too many, or too few, primary rate channels is a familiar problem for many businesses).

BT estimate the final closure of ISDN will be in 2025, but as Information Age magazine recently wrote: “with millions of customers to migrate and little further investment in the existing ISDN lines likely to take place, switching to more sophisticated SIP technology should be a priority for businesses.”[1]

Perhaps most importantly, legacy PBX systems are increasingly not fit for purpose with respect to the modern, agile business environment; offering insufficient flexibility, and little support for integration with mobile telephony and other enterprise applications. Upon closer inspection many businesses find that their aging telecoms system has effectively become an ignored silo within the organization with many employees (especially millennials) by-passing it entirely to rely on their smartphone, an option that could be costly.

What is the alternative?

The future lies in the migration of all voice and data telecommunications to the Internet or private converged networks and embracing what’s called an ‘all-IP environment’. In these scenarios, legacy PBXs are replaced with IP-based systems that support ‘virtual’ phone lines using SIP Trunking and Voice over IP (VoIP).

With an IP-PBX, a business can continue to make old-style PSTN calls where necessary, whilst integrating highly flexible, feature-rich VoIP, operating over existing organisational LAN and WAN networks. IP-PBX not only provides a more flexible base, with better functionality, but also may offer a lower total cost of ownership.

This process of modernisation – in the industry jargon, ‘getting beyond the dial-tone’, provides a future-proof, Internet-based foundation for next generation unified communications (UC) which bring together office and mobile telephony, video conferencing, social media, enterprise apps and cloud systems.


activereach offers a comprehensive telephony infrastructure service, helping organizations realize business goals and move on from legacy PBX and ISDN systems. Our vision is that that every company, regardless of size, should have the opportunity to access the latest in low-cost, future-proof, voice services using IP-based technology.

activereach’s advanced telephony service features include:

  • Site surveys and strategic reviews of the sustainability of an organization’s telephony system; reducing operational risk and decreasing operational costs.
  • Advice on rationalizing voice and data infrastructure including large, or multi-site, user migration strategies.
  • An end-to-end service to assist in the smooth transition from legacy PBX/ISDN to modern, IP-based telecommunications.
  • The design, supply, configuration and support of key infrastructure such as SIP trunking, VoIP, IP-PBX, gateway systems and desktop handsets.
  • Direction on moving from dedicated hardware PBX assets to modern, low maintenance, software-driven infrastructure.
  • Advice on integration with enterprise apps such as CRM, cloud systems, and modern, unified communications services including HD video conferencing and social media.
  • Consultancy on voice call security, resilient topologies, and disaster recovery strategies.

[1] Rossi, Ben, ‘10 years to go: what the end of ISDN means for your business’, Information Age (25th Sept. 2015),, accessed 6th Apr. 2016.

To find out more about moving on from legacy PBX and ISDN systems to IP telephony solutions from activereach, please call a Networking & Security Specialist on 0845 625 9025.