the X-Mon inserts the TB Mic into the Cue paths in when you press the TB to Cue so: cue mix out of PT into Cue input #1 press TB to Cue#1 Your voice comes out Cue#1
There is a TB output on the X-Mon. Is this for sending to a 3rd cue mix by any chance? I found the TB out existed after a session I needed a 3rd cue mix for. It's on the D-sub for the mini monitors, listenback mic, etc. (I think)
Use the Talkback Slate output on the TB/LB/util connector on the back of the XMon. It is always on and is the sum of the Internal TB and External TB post Volume and mute. The talkback is not really user accessable from the DB15 Control snake.