SL mode on the F70 is said the be the forerunner of the boost process on the F75se and the T2se. It cranks up the power quite a bit! Not good for trashy sites though...sampling rate seems to be slower (hence the SL, i reckon!). On a fringe target though, switching to SL can give enough power to get an accurate ID.OK - My CZ6a had a boost setting which gave extra depth so Fisher must be keeping the idea.