Minelab F3 Mine Detector Operation Manual page 34

NOTE
Maximum sensitivity is only available 30 seconds after the Threshold
Tone commences. Do not test the detector with the Test Piece until
30 seconds after the Threshold Tone begins.
 Black Sensitivity Endcap:
Hold the Test Piece above the middle of the coil with the rounded
end (containing metallic target) AWAY from the coil.
Move the Test Piece towards the centre of the coil until it lightly
touches the surface then move it sideways off the coil (the Test
Piece should be moved slowly and smoothly during this procedure).
A faint but clear response (change in Threshold Tone volume and
pitch) should be heard indicating the sensitivity of the detector is
correct.
Figure 20: Test Piece Procedure
 Red Sensitivity Endcap:
Hold the Test Piece above the middle of the coil with the rounded
end (containing the metallic target) TOWARDS the coil.
Move the Test Piece towards the centre of the coil until it lightly
touches the surface then move it sideways off the coil (the Test
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