When putting a vanilla Redstone Comparator next to a drawer, I would expect it to output a redstone signal proportional to how full the drawer is, but instead nothing happens. I know there is the Redstone Upgrade which works the same way in most cases, but not for 2x1 and 2x2 drawers : the Redstone Upgrade gives the level of fullness of a specific slot, while the Redstone Comparator gives the level of fullness of the entire storage block.