Minelab F3 Mine Detector Operation Manual page 32

 The F3 will emit a series of four rising tones over 12 seconds
(internal diagnostic checks occurring).
At the completion of the Start-Up Tones a low volume Threshold
Tone will remain audible.
 If the Threshold Tone is steady continue with STEP 2. If the
Threshold Tone is noisy or uneven when the coil is stationary,
perform a Noise Cancel (Section 6.3.a).
 If the Threshold Tone is steady but seems louder than normal
when the coil is away from the ground and metallic targets,
perform an Audio Reset (Section 6.3.b).
b. STEP 2
 Ensure this procedure is carried out on ground free of metal and
hold the coil about 150mm (6 ins) above the ground.
 Press down and hold the green Ground Balance button
and slowly lower the coil directly to the ground then lift the coil up
again 150mm (6ins). Refer to Figure 19.
 Continue to slowly lower and raise the coil until the „Ground
Balance OK‟ tone is heard. („Ground Balance OK‟ tone consists
of a short high-pitched double beep).
 Release the Ground Balance button.
Figure 18: Switch On
Ground Balance
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