“At its core, the card harvests energy from light, radio, and/or a USB connection to enable the blinking of LEDs.”[0] So the last is USB, the sneakily obvious

“At its core, the card harvests energy from light, radio, and/or a USB connection to enable the blinking of LEDs.”[0] So the last is USB, the sneakily obvious one. 0: https://www.keacher.com/xmas24/tech_info.htm https://www.keacher.com/xmas24/tech_info.htm