Detector is rechargeable with Ni-MH (9VDC-200 mA) battery. It should be recharged with its (220 VAC/12VAC-16mA) charger when yellow LED(LOBAT) is on. First charging period is approximately 15 hours. Later charges are 12 hours. The battery is replaceable.The warning tone may be heard when the detector is operated. Then the tone should be adjusted to a min. audible signal level by sensitivity potentiometer for highest sensitivity. The detector is normally silent until metal is detected. Detector then sounds and audible and visible (red LED) alert, depending the size of the metal such as guns, knives razors or even a key. Sensitivity may be lowered by level potentiometer to avoid misfunctioning for some items such as money, key etc The detector can be safeley used for a very long period, compared to its contemporary equivalents since it is activated by push button only during scanning. Technical Features High sensitivity and selectivity Wide scanning area Easy to use Automatic frequency locking Improved technology Portable and comfortable cover NiCd Battery (with charging led) Earphone output and earphone (optional) Vibration (optional)