We are almost finished migrating a couple hundred Cisco 7940 and 7941 phones from Cisco Call Manager to 3CX and we are encouraging everyone to upgrade their Cisco phones to Yealink phones over the next year. But we've run into a problem. Cisco phones can't transfer calls to Yealink phones. On a Cisco 7941 Answer a call, press Transfer, dial extension of Yealink phone, Yealink user answers, press transfer again. The call fails to transfer and the call from Cisco to Yealink is stuck, the Cisco user can't hang up on that call. They are able to resume the original call though and the original call stays on hold. It happens the same way from a Cisco 7940 when you use the Transfer button. The Blind Transfer button however does work when transferring calls to Yealink phones. Both methods of transferring work when transferring to another Cisco phone on 3CX. I am aware of the issue where you cannot blind transfer from a 7941, if you press transfer a second time before the other user answers, it will drop that call. In this case the other user does answer before pressing transfer a second time.