Pyle PHMD3 Instruction Manual page 7

4. Learn to use the ALL METAL mode.
Set the MODE switch to ALL METAL, and SENS to "10".The DISC/TONE
knob is useless at this time.(Fig.10).
 Sweep the metal samples you prepared 2 to 3 inches(5-8cm) above the center
of the search coil in turn, the detector will respond with a "DI" tone, and the
pointer will swing to the right for one time.(Fig.11)
 Note: You have to move the metal objects, as the metal detector is in the
motion mode. If you don't move the metals, the detector will not respond.
 When rotate the SENS knob from "0" to "10",and change the height of the
metal samples in the same time, you will find that the sensitivity of the detector
becomes higher.
Figure.10
Figure.11