Featuresr 2 functions in one speaker and bicycle tail lightr press the key twice quickly to start or shut down the bluetoothr two patterns for start up one for indoorwhite light one for outdoorred green or blue lightr when riding bicycle at night the light sensor will start up the alarm light automatically for reminding other peopler when you forget to turn off the system detects no riding action and bluetooth play it will enter into dormancyr the bicycle speaker tail light is r