Garrett Metal Detector GTI 1500 Owner's Manual page 30

Press + to increase sensitivity. Press -
to decrease. A single touch and release
adjusts the level in a small increment.
Continuous pressing results in a continu-
ous adjustment.
Threshold
Press the MENU touch pad to display
THRESH on the screen (above, with fac-
tory setting indicated on Upper Scale),
and you can use the + and - touch pads to
adjust the threshold of sound that is being
produced by the GTI 1500 as it scans.
Multiple touches will increase or decrease
the sound level. Changes can be seen on
the Upper Scale.
You can search silently or at any level of
constant sound. Charles Garrett and veter-
an hobbyists usually prefer to operate the
instrument at a minimum level of audible
sound but this is no longer necessary.
0 - Garrett Metal Detectors