5pcs HC SR04 Ultrasonic Ranging Module Distance Measuring Sensor Transducer for Arduino Features: This module can accurately measure distance by using ultrasonic ranging principle. It can compete with foreign ultrasonic ranging modules such as SRF05 and SRF02. High precision distance measurement, super close blind zone(2cm). Stable performance, high reliability. This module is completely compatible with GH-311 anti-theft module. Specification: Operating Voltage: DC5V Static Current: <2mA Level Output: High 5V, Low 0V Sensing Angle: ≤15° Detecting Distance: 2cm-450cm Accuracy: 0.3cm Wiring: VCC, trig(control terminal), echo(reception terminal), out(empty), GND   Module Working Principle: 1. Adopt IO trigger through supplying at least 10us sequence of high  level signal. 2. The module automatically send eight 40khz square waves and  automatically detect whether receive the returning pulse signal. 3. If there is signals returning, output high level through IO, the  continuance time of high level is the time of that from the ultrasonic  transmitting to receiving. Measuring distance = (high level time * sound  velocity (340M/S) / 2.   Package list: 5 x Ultrasonic Ranging Module   Note:  1. The module should be inserted in the circuit before power-on, which avoid producing high level of misoperation; If not, then power again. 2. The TRIP pin is an internal pull-up 10K resistor. Pull down the TRIP pin by the IO port of the microcontroller and give a pulse signal of 10us or more. 3. The OUT pin is the switch output pin when the module is used as the anti-theft module. The distance measuring module does not need this pin!