Batt-O-Meter Guitar Pedal and Preamp Battery Tester Designed to quickly save performers time and stress before relying on a battery on stage or in studio Reads how many volts a battery is delivering Reads hours left before the device runs out of power Checks the remaining life in any 1.5-volt or 9-volt battery Convenient slide switch differentiates between Alkaline, Rechargeable, and Carbon Zinc batteries Designed to quickly save performers time and stress before relying on a battery on stage or in studio Reads how many volts a battery is delivering Reads hours left before the device runs out of power Checks the remaining life in any 1.5-volt or 9-volt battery Convenient slide switch differentiates between Alkaline, Rechargeable, and Carbon Zinc batteries. Please refer the User Manual before use.