Rainbow remote extension not ringing when main set is out of service

Hello,

We have followin set up:

1 x IPDS = tandem main set

1 x Remote Extension = tandem secondary set --> rainbow extension

The IPDS is an ACD Station.

When there's no ACD Agent logged on the IPDS, everything is working fine (incoming/outgoing calls possible from the IPDS and from the Rainbow client when set to Computer (VOIP).

But when an ACD Agent Logs on to the IPDS:

- incoming calls: only the IPDS rings when calling the IPDS extension.

- outgoing calls: possible from Rainbow and from the IPDS

I validated the parameters "Ring when main set is OOS" in System Parameters, and in Telephony Features COS.

The way I see it: if an ACD Agent logs on to the IPDS, the IPDS extension essentially becomes unavailable --> the secondary set (the Rainbow remote extension) should be able to answer incoming calls --> this is not the case.