This programming cable is designed for quick and easy programming of Vertex Standard VX-P921 radio. The power supply is done over the USB interface. The internal converter circuit board (interface) mounted inside the USB shell. This cable does not include any manuals or instructions for use. Therefore, it will be assumed that the purchaser is knowledgeable in using the cable for the applications it is designed for. Please note that we supply the hardware only, we don’t supply the programming software.