Garrett AT Pro Owner's Manual page 10

9. If desired, attach headphones to the 2-pin connector
of the Control Housing.
Note: Headphones are not required but are desired
by many hunters to hear faint targets. Connecting
the headphones will silence the detector's speaker.
Note: The provided headphones are for dry use only;
see page 54 for optional waterproof headphones.
10 Garrett Metal Detectors