This is a test fixture and charging station for the Duet battery and board assemblies. While Duet can charge just fine on a computer USB jack, this kinda becomes a bit of a challenge when you need to charge 1000 of them. We just finished this little fixture that can charge 80 at a time. You will note on the video a lot of little flashing lights. We are working on a charge monitoring system that is fully aware of the Duets charge status. When charging it blinks slowly at the beginning, faster towards the end, then when fully charged the LEDs stays on.