It's a small USB to TTL serial tool, using the PL2303 chip. You can use it to connect some serial device to your PC via USB port. Features: Compatible with 32-bit & 64-bit Windows, Mac OS 8 to OS X, Linux and Android! To test the unit use the shunt to connect TX and RX (loopback test) 3.3V and 5.0V outputs are available to power your project directly from the adapter. Part List： 1 x USB to TTL module