Scope:Mainly used in battery (9V or 12V) voltage monitoring, simple and practical, support sound and light alarm.Features:When the buzzer low voltage will "DiDiDi" sounds and the red LED lights up, when the battery voltage rise above to the set value, buzzer will stop alarm.Size: 2.9 x 3 cmThe main chip: LM3589V Battery: When a battery over-discharge (battery voltage drops below about 8V), the red lights and the buzzer calling to achieve sound and light alarm, to achieve control battery discharge status, prevent over-discharge battery, and damage battery;12V Battery: When a battery over-discharge (battery voltage less than 10.4V), the red lights and the buzzer calling to achieve sound and light alarm, to achieve control battery discharge status, prevent over-discharge battery, and damage battery;Advantages:With a sound and light alarm, simple and practical.The module input with reverse protection, if reverse polarity power input will not burn. But without overvoltage protection, if the input exceeds 15V, the chip above the module will burn out.Adjustment method:9V Battery: Input 9V, the LM358 voltage adjustment between 2 feet and 4 feet to about 5.78V, the alarm voltage is 8V (we has set it before shipment, so you don't need to adjust it again). Clockwise adjustment, 2 feet and 4 feet voltage is reduced, the sensitivity increased.12V Battery: Input 12V, The LM358 voltage adjustment between 2 feet and 4 feet to about 6.05V, the alarm voltage is 10.4V (we has set it before shipment, so you don't need to adjust it again). Clockwise adjustment, 2 and 4 feet voltage is reduced, the sensitivity increased.Package includes:3 x Battery Over-discharge Protection Module