First time I used it I was unsure how well it would work so I plugged in my head phones to it, put it in my pocket, wore another alti, seconds after I left the plane I heard a nice voice saying "13,000". then "12,000". "11,000" and so on, at 5,000 I heard "Break off" and at 3,000 she said "deploy, deploy". under canopy the voice told me "down wind", "Base", "Final". never had to look at my alti, I always wear an extra to be safe but its awesome