This little double sided PCB is a galvanic insulator for the popular Atmel ISP MK2. It uses the ADuM1401 and ADuM5000. One wire for the 5V supply needs to be loosely connected. Thanks to the ADuM5000 on the hidden bottom side it doesn't need the VCC supply on the AVR side. The only precation that needs to be taken in account is that the outputs do not get set to high impendance if the reset is high.