Details: The AT Pro features advanced, proportional (Pro) audio modes. This allows the user to hear subtle changes in a target’s response. Proportional audio also helps the user to better judge a target’s size, shape and depth and has the additional benefit of a much faster recovery time when detecting adjacent targets. The AT Pro also includes three Standard audio modes, which provide a full-strength beep regardless of a target’s amplitude. Many detectorists prefer this simpler, binary (either on or off ) target response.