The USB3-EXT-16 is an active extension cable which can be cascaded (up to 5) to extend the distance between USB devices and a PC. It regenerates the USB signal for maximum reliability and performance over extended distances. Can be used without a power supply when cascaded up to 2 devices maximum otherwise the power supply is required at the farthest connection from the USB source. Power supply purchased separately here. http://hallresearch.com/page/Products/511-41052-1305