... " gradually increasing or decreasing disappear even, press the button to put "critical sound" restore again ... target instrument will continue ring.the pointer will deflectionHow to adjust the sensitivityTurn the level to ground balance, ... 10-15 cm,if the ring up ,up the palte and press the key ,then turn knod ... not iron,just test the response to iron , if the ring up ,up the palte and press the key ,then ...