Each buzzer consists of an Arduino Pro Mini 3.3 V, a nRF24L01, and of course a big pushbutton on the top.

The creator of the Arduino RF Pro Mini open source development board Etienne, explains a little more about the inspiration behind the project. “ I’ve loved Arduino for years.

Removing the Arduino Pro Mini’s voltage regulator and two LEDs got the current down to 18 milliamps and a recording time of 9 hours. Better. Those are the highlights.