Better than I originally thought!
I just left a review asking people if this worked outside in a windy field - shame there isn't a q&a section on this site! Anyway I wanted to come back and alter my original 2 stars as I didn't have confidence because I couldn't hear it but low and behold I called my dog in from outside using it so I can confirm it does work! It's just a bit weird at first as the ones I used in training I could hear too so that gave me more confidence in the product! Please accept this resubmission of my review as I feel I was unfair the first time round!