AdvantageMechanical Drive:It is a practical and economical spring alarm without battery.Automatic Ring:The bell will automatically ring when it rotates to setting time.Operations1.Clockwise Rotate to the 55 minutes2.Counterclockwise Rotate to time point you want to set up.If you want to set fixed time to 20 minutes,just rotate in counterclockwise direction to the 20 minutes point.3.When time's up,it rings automatically.ParametersOperating Temperature:-10℃～+55℃.Operating Angle:360 degree.Ringing Time:Based on the timing range,timing range is ,rlonginging time will be long.NoticePlease do not rotate the timer vigorously and repeatedly,in case that the built-in movement parts are destroyed.The best Father's Day gift, Mother's Day gift, Thanksgiving Day gift, Christmas gift