OK. On some models, the disc. control had to be clicked to the "on" position to begin the tones. Others had just the "tone" position on the 3 way toggle. In either case, rotate the disc. knob until the nickel goes from a high-then mixed- and FINALLY a smooth low tone. You're set. Coins will give a high tone, tabs a broken tone*(except the sta-tab), and nickels a low tone. Also, what Digger said on the large targets=raise the coil and you'll be able to tell if it's a large target. Also, coin-sized targets give a fast, short, "dink" while the larger targets give a rather lengthy high tone.