Business telecommunications and IT systems

On July 31 2007, BT is withdrawing two versions of their ISDN which will affect many businesses. Customers using these ISDN versions will have their circuits (exchange lines) ceased and will not be able to make or receive phone calls.

BT has 5 ISDN versions.

• ISDN30 with DASS2, launched in 1985.
• ISDN30 with 'Limited I.421', launched in July 1995 - to be withdrawn
• ISDN30e with full I.421, launched in January 1999

• ISDN2 with 'Modified I.420', launched in 1985 - to be withdrawn
• ISDN2e with full I.420, launched in October 1997

What is 'full I.421' and 'full I.420'?

These are methods of dialling (signalling) on ISDN. Full I.421 and full I.420 are the only versions which fully comply with the European Telecommunications Standards Institute (ETSI) accepted signalling standards.

What's happening to ISDN30 with DASS2?

Although DASS2 does not comply with ETSI standards, BT is keeping this signalling for the foreseeable future. Many of their larger customers use DASS2.

How can I check for certain if I am affected?

As a BT Gold Partner, du Pré can do this for you, quickly. Contact us on 01635 55 55 32 and we will be able to confirm the situation for you.

If I am affected, what do I do?

If you use ISDN30, we can upgrade your ISDN circuit to the latest version. It is unlikely you will need to change your telephone system.

If you use ISDN2, we can upgrade your ISDN circuit, and you will probably have to upgrade your telephone system to make it compatible. Again, du Pré can advise.

What if my ISDN is not from BT?

There is no problem! It is a BT issue only.