PAC BG-12 Battery Guard Indicator and Load Shut Down Protects Voltage System In Vehicle When Power Is Dropped Below 11.6 Volts Battery guard Keeps battery from draining Battery Monitor Microprocessor that constantly monitors the voltage available LED changes color with state of battery: green at 12.4v or higher, yellow below 12.4v, red at 11.5v or lower Below 11.6-volt the monitor turns off the vehicle's sound system Progressively resets as battery recharges, turning the head unit back on at 12.4-volt