Is Your Business Still Using ISDN?

In 2017 BT Openreach announced that it would be switching off both PSTN and ISDN networks by 2025. That gave businesses eight years to change to a modern alternative for their telecoms. It’s anticipated that BT will put more pressure on businesses from 2020, although there are clear advantages to moving right now.

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Here we take a look at what ISDN is, how businesses are responding to the announcement, and the benefits of upgrading.


ISDN has been in use for digital transmission since the 1980s. Businesses found that ISDN gave them a high-quality service for both speech and data simultaneously on the same lines. The lines could be leased in increments of 64kbps and used for Internet access, typically at 128 kbps in both directions.

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There are two options for replacing ISDN: SIP and VoIP. Here we will look primarily at the preferred option – VoIP.


Voice over IP (VoIP) is a cloud-based solution that routes phone calls, videoconferences, etc over the internet. This gives businesses a raft of additional features over ISDN:
– Telecoms costs are much lower
– Modern technology is easier to maintain and user-friendly
– Ramp up and down the number of users
– Employees can work from home or in any regional office
– As the system is cloud- and software-based, new features and upgrades are regularly introduced
– VoIP integrates with other systems
– Businesses find that better communication boosts their productivity

So are businesses taking note of the need to change? There has certainly been a decline in the market for ISDN, and businesses are seeing communications technology as a key factor in improving efficiency. However, there are still an estimated two million firms using ISDN, and it’s believed that 25% of businesses are not aware of BT’s plans. Ofcom reports that there are still 32.7 million exchange lines.

Choose a Supplier

Choosing a supplier for VoIP is a key part of switching. There are many suppliers offering cheap AZ termination, but it’s important to ensure good value for money from a trusted supplier such as

If your business is still using ISDN, look out for pressure from BT Openreach, encouraging you to upgrade. Moving to VoIP is a sound business move – not just to join the herd being prodded along by BT but to gain real business benefits from the technology.