SainSmart HC-SR04 Ranging Detector Mod Distance Sensor (Blue) Using IO trigger for at least 10us high level signal The Module automatically sends eight 40 kHz and detect whether there is a pulse signal back IF the signal back, through high level ,time of high output IO duration is the time from sending ultrasonic to returning. Test distance = (high level time velocity of sound (340M/S) /2 Power supply :5V DC, quiescent current : &lt;2mA,effectualangle: &lt;15 ranging distance : 2cm~500 cm resolution : 0.3 cm