VOIP Tech Chat → BT ISN30 and Fibre

We have a Avaya VOIP system in the office that we were sold ages ago. This is run over ISDN30 and the cost is over £150 per month.

My question is why can't we use this phone system over ADSL or fibre ? The overal speed on fibre would be significantly more and the cost would be about 1/3.

ISDN30 aka PRI ISDN aka E1 (the European version of the T1) can carry 30 voice channels directly, 2.048 mbps of data, or a mix of both. Without knowing if your phone system uses the voice channels directly or uses VoIP over the E1 (configured as all data) we cannot say. When configured for voice channels it's basically a POTS trunk and has no relation to VoIP.

Even if your phone system uses VoIP over the (data) E1, SLAs with a guaranteed MTTR like what's on the E1 are not cheap and you will probably not even be able to get one on an ADSL line. Commercial grade fiber service should have it, but will most likely be more expensive then the E1.

/M