Minelab F3 Operation Manual page 32

F3 Operations Manual
NOTE
Noise Cancel and Audio Reset procedures can be performed at any
time the Threshold Tone becomes noisy, uneven, or rises in volume.
Having completed STEPS 1, 2 and 3 the F3 remembers the Ground
Balance setting even after the detector has been switched off.
After Noise Cancel is completed the F3 remembers the frequency
selected to minimise interference, even if the detector is switched
off.
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