eFuture(TM) HC-SR04 Ultrasonic Distance Measuring Sensor Module Fit For Arduino +eFuture's nice Keyring

Note:
1>The module should be inserted in the circuit before been power,which avoid producing high level of misoperation;if not,then power again.
2>This module is not suitable to connect with electric power, if you need to connect this module with electronic power,then let the GND terminal of this module to be connected first,otherwise, it will affect the normal work of the module.

Module Working Principle:
Adopt IO trigger through supplying at least 10us sequence of high level signal.
The module automatically send eight 40khz square wave and automatically detect whether receive the returning pulse signal.
If there is signals returning, through outputting high level and the time of high level continuing is the time of that from the ultrasonic transmitting to receiving.

Package include:
1 x HC-SR04 Distance Sensor Module.
1 x eFuture's nice Keyring (with eFuture's logo)