 If you see a horizontal battery symbol at the top of the screen, the fine-tuner Echo battery is running low. Using a large coin, turn the battery compartment cover until it points to the unlocked symbol. Carefully remove the cover, making sure the black silicone ring does not fall out. Remove the old battery, then insert a CR2032 battery with the positive poles facing upwards. Place the cover over the battery compartment, pointing towards the unlocked symbol. Using a coin, turn the cover until it points to the locked symbol.