Here's some more details of the fault.

When buttons for lines 1 or 2 are pressed to get an outside line the phone appears to work as normal but there is just silence, i.e. no dial tone.

We have 2 x ISDN 2e boxes and I've tried swapping the RJ45 cables across (as suggested in another thread on this forum) to test if there's a problem with the incoming lines, however the system behaviour was still the same.

Edit: I must be losing my marbles as I swapped the cables again and the fault moved so now lines 1+2 work, I guess this indicates a line fault and not a system programming issue. I've logged a fault with the supplier, fingers crossed!

I've also tried swapping the 2 red cartridges around but once again the behaviour still remains the same.

Both accesses are set as P>P and are configured as T interface, in fact the settings for both accesses are identical. I've tried both accesses as P>MP seperately and together but to no avail.

Edit: The T/S settings on the handset allows only the setting for access2 to be modified, as I was using the Versatility software I hadn't noticed. Not sure if this is normal.

I'm beginning to feel that I've tried most of the options with no improvement, I even undone the work to set up the DDI and that made no difference.

I think I can feel a bald spot growing on my head!

All fixed now, it turned out to be an external fault which just happened to rear it's ugly head at the same time as I added the DDI number!

@Lectrician: Thanks for the tip, I found that changing the P>P/P>MP setting on the programming handset automatically re-booted the system and with the software editor it automatically re-boot when disconnect was clicked. I also found your answers in other threads on this forum proved very useful when fault finding.

Best regards,
Graeme