Universal Serial Bus (USB) is a royalty-free bus specification developed by leading manufacturers in the PC and telephony industries to support plug-and-play peripheral connections. USB offers increased bandwidth, isochronous and asynchronous data transfer, and lower cost than conventional input/output ports. Designed to consolidate the cable clutter associated with multiple peripherals and ports, USB supports all types of computer- and telephone-related devices.
Before the arrival of Universal Serial Bus (USB), adding peripherals required skill. You had to open your computer to install a card, set DIP switches, and make IRQ settings. Now you can connect digital joysticks, scanners, speakers, cameras, or PC telephones in seconds. Instead of opening up your CPU to insert new boards, you make all the connections outside the case to the USB port. USB detects and configures the new devices instantly.
USB offers the convenience of hot-swappable connections, so you can attach or remove peripherals without shutting down your computer.
USB hubs have additional ports that enable you to daisy-chain multiple devices. The USB daisy-chain can support up to 127 USB hubs and peripherals less than 5 meters apart.
USB is almost eight times faster than T1. And more than 450 leading manufacturers of PCs, peripherals, and software support USB.
Currently, USB consist two major revisions:
