How a USB Works: the Inside of the Cable: 3 Steps Strip an end of the USB cable, remember to leave a USB port on one end, show the wires inside (with their coloured covers). The wires should be the same as in the photo below, the red wire = 5 Volts (+) and the black wire is the ground (-), for now ignore the other two wires I will hopefully make an instructable about them at a later stage. USB Connector Pinouts - HobbyTronics USB Connector Pinouts. USB is a serial bus. It uses 4 shielded wires: two for power (+5v & GND) and two for differential data signals (labelled as D+ and D- in pinout). In a USB data cable Data+ and Data- signals are transmitted on a twisted pair with no termination needed. Half-duplex differential signalling is used to reduce the effects..