I have a scenario where calls that are transferred to a shared line doesn't trigger the "in use" light to show up on both phones that have the shared line.  but when i make an outgoing call, let's say, using the shared line, the "in use" light lights up on both phones that have the shared line.  Phone - polycom 650s. Just a noob with SIP, kamailio and telecom, so not sure where to start debugging.  Any suggestions would be appreciated.  thanks in advance for your time.