This is a pure CUCME environment, not CUCM... also a bunch of small 521SG phones and a UC500.
We put the Callback softkey in a ephone template to be part of everyone idle o seized telephone state. It works on single or huntstop channel lines, but we noticed that there has only ONE ring to the phone which initiates the callback. The customer need more than that, because it's too short to be noticed when several other phones are nearby.
Is it possible to configure callback ring duration?
I haven't found anything... and the customer is annoyed about a brand new system less efective than the old one, which has a perfect callback feature... also when the other line isn't busy anymore, it calls originator first, UNTIL you hold off, then it calls the other party... connect.