i was going through the hidden menus on the radio (hu-615) and went through the one where you turn it off and press and hold the power button while turning it back on and seen diver test and turned it on to see what it was and then i seen a 2 at the top next to fm and when on fm it switched between 1 and 2. pressing the auto button gave option for auto, sub, and main which made the auto made the 1 and 2 switch automatically and sub was i think 2 and main was 1. anyways i was just wondering if anyone knew what this means and what it does. i tried looking it up and couldn’t find anything.