The ISDN switch off explained
ISDN is being withdrawn alongside the analogue network. If your business still runs ISDN2 or ISDN30, those lines stop working after January 2027.
What ISDN was, and why it is going
ISDN carried digital voice and data over the copper network, and for a long time it was how any serious business connected a phone system to the outside world. Multiple simultaneous calls, reliable quality, direct dial numbers.
It is going because it runs on infrastructure being retired, and because everything it did is now done more cheaply and more flexibly over an internet connection.
How to tell if you have it
ISDN2 or ISDN30 will be named on your bill. If your phone system is a box on the wall installed more than eight years ago, ISDN is likely. Larger sites tend to have ISDN30, smaller ones ISDN2.
Two routes
What replaces it
SIP trunks
if you want to keep your existing phone system. The trunk replaces the ISDN line and the system carries on. Usually the cheapest route if the system is still fit for purpose.
Hosted voice
if you are ready to replace the system too. The phone system moves to the cloud and you pay per user.
Both keep your numbers.
Common questions
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ISDN is being withdrawn alongside the analogue network. If your business still runs ISDN2 or ISDN30, those lines stop working after January 2027.
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ISDN carried digital voice and data over the copper network, and for a long time it was how any serious business connected a phone system to the outside world. Multiple simultaneous calls, reliable quality, direct dial numbers. It is going because it runs on infrastructure being retired, and because everything it did is now done more cheaply and more flexibly over an internet connection.
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ISDN2 or ISDN30 will be named on your bill. If your phone system is a box on the wall installed more than eight years ago, ISDN is likely. Larger sites tend to have ISDN30, smaller ones ISDN2.
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SIP trunks if you want to keep your existing phone system. The trunk replaces the ISDN line and the system carries on. Usually the cheapest route if the system is still fit for purpose. Hosted voice if you are ready to replace the system too. The phone system moves to the cloud and you pay per user. Both keep your numbers.
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Check the bill. Check whether the phone system supports SIP. Get a comparison of both routes. Start early, because porting numbers takes weeks.
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Your existing provider should be able to advise. If they cannot, a telecoms reseller will handle the migration end to end.
What to do
Check the bill. Check whether the phone system supports SIP. Get a comparison of both routes. Start early, because porting numbers takes weeks.
