Targethobby 3 IN1 Low Voltage Buzzer Alarm & Discovery Alarm & Discovery Buzzer & Signal Loss ALA Battery monitor function :Hold the button 3 seconds to enter the setting of the voltage threshold;Press button to set the alarm threshold between 3.4~3.7V/Cell(red LED);The value will be saved & exit if no action within 10 seconds Discovery buzzer function : It is easy to use the function, Just plug it in one Aux channel(e.g. Gear). Move the toggle switch to one side or another side, the BM3in1 will alarm BeBeBeBeBe & blue LED blink Signal loss alarm function : It can warn you if you turn off the transmitter first by mistake, if you have trouble finding a model in the long grass Please see the manual as the last picture on the left