Garrett Metal Detectors Metal Detector GTI 1500 - Manual (Page 31)

The audio will increase sharply when-
ever a desirable target is encountered.
(Remember, a cursor will indicate every
target.) When headphones are used, it
will usually be necessary to decrease the
threshold level since sound is more audible
through headphones.
Frequency
This detector is capable of operating at
four different detection frequencies or
channels, which you will find valuable if
you participate in competition hunting or
if you enjoy hunting with others. In fact,
operating your GTI 1500 at a different
frequency might be necessary any time
two or more detectors are being used so
close together that their signals interfere
with one another. Outside electrical or
atmospheric interference can also cause
an interference that results in strange
sounds.
Graphic Target Imaging 1500 - 1