Universal Serial Bus (USB) is a communications architecture that gives a personal

computer (PC) the ability to interconnect a variety of devices using a simple four-

wire cable. The USB is actually a two-wire serial communication link that runs at

either 1.5 or 12 megabits per second (mbs). USB protocols can configure devices

at startup or when they are plugged in at run time. These devices are broken into

various device classes. Each device class defines the common behavior and

protocols for devices that serve similar functions. Some examples of USB device

classes are shown in the following table