Put it behind ear, Alerts when the for head lower in the degrees of 15° to 20°. Especially suitable for long-distance driving or night driving. Driver alarm can help accidents caused by sleep when driving. Examine whether it is in the normal :it beeps when you are leaning your for head forward and makes no sound while sitting straight , it is at normal . It is suitable for a wide of people, such as night shifts, door guards, guards, television stations, radio stations, night broadcasts of personnel, and security personnel.