Hot rocks do not register, as they have been somewhat ‘notched’ or inhibited. This trick gives you good stability regardless of the ground rejection level, however it also deprives you of the benefits of a well-adjusted ground balance, and worse, gives you the impression that your settings are well configured.
Very often the deepest targets in magnetic soil are identified with a signature similar to that of hot rocks, and are therefore detected poorly with this kind of device (as they are ‘notched’).
DEUS on the contrary gives you full control over the ground settings. When you lower the ground balance (87-85-82 etc.) you fully accept hot rocks, which is the only way to obtain real gains in terms of penetration on certain magnetic soils.