Currently using Lync 2010 with a Sonus SBC 2000 gateway and Polycom CX600 phones. When we are starting a group call we are not getting ringback tones when adding people to the call. So users are complaining that they are unsure if the person they are trying to add are actually being called. Is this something that can be changed on the gateway? Thanks in advance for any suggestions/help.

Hi,

It seems to be the expected behavior. For Lync Server side, there is no way to add ring back tone when adding people to a group call.

Here is a similar case may help you:

https://social.technet.microsoft.com/Forums/en-US/0e1be655-bdaa-4268-b843-8aa652855dfc/conference-call-no-ringback?forum=lyncvoice

Best Regards,
Eason Huang