Garrett GTI 2500 Owner's Manual page 54

Press the proper (+) and (-) pads until
audio does not change or changes only
slightly when the searchcoil is lowered
to operating height. The Ground Balance
value that you have set for the detec-
tor will not change as long as Auto Track
remains turned OFF. Whenever Auto Track
(see below) is operating, it will govern
the ground balancing function of the GTI
2500.
When searching over extremely mineral-
ized soil, it is recommended that you hold
the searchcoil at least two inches or more
above the ground. You will not lose depth,
but will actually detect deeper because
ground mineral influence will be greatly
reduced.
Auto Track
This Search Aid permits the detector to
maintain optimum ground balance auto-
matically, regardless of hanging mineral-
ization or other conditions. There are three
tracking speeds: slow, medium and fast.
Use slow tracking when scanning over
ground with consistent mineral conditions
5 - Garrett Metal Detectors