Hello!
Thank you Raymond about your explanation, but I dont agree with some point:
If it really need an answer about your question -- "if it is possible to move calls back". I think it's unnecessary. - in my case I have two not equal servers, so I need to have only one as a master.If switchover happens I need to have ability to restore master back.
Thank you Luis for your link, you can do simple test to understand what I am talking about: do call -> check on master and slave #show channels -> restart FS on slave -> check on master #show channels. In my case I dont see any active calls after this, so restoring back is not possible.