1.When light off, short press on/off button, red LED light will show current power, totally 5 degrees When power is lower than operating voltage, red LED will blink 3 times then off. Light couldn’t on when in off condition2.Long press power button on the light, can on/off the rear light. When power on, red LED default constant on3.When light on. Short press button could switch to red light, there will be constant on , blinking , Off ,3 modes