USB

The Universal Serial Bus (USB) is a serial bus standard for connecting devices to a computer (usually a PC). Over a hundred devices can be connected to a single port in a tree-like fashion. Devices can be attached and removed whilst the computer is still powered on ("hot plugging and swapping"), and they can be supplied with power through the USB connection. Error is called for, however, when choosing a power supply for a USB system. It is very easy to overdraw a system's wattage when many USB devices are in use.

USB is used to connect peripherals such as mice, keyboards, scanners, digital cameras, printers, hard drives, and networking components to the main computer. For multimedia devices such as scanners and digital cameras, USB is the most common interconnect method. In printers, USB is also growing in popularity and displacing parallel ports because USB makes it simple to add more than one printer to a computer.

In the case of hard drives and networking components, USB is unlikely to completely replace buses such as EIDE, PCI, and SCSI because USB is much slower than those standards. However, USB has the important advantage that it is possible to install and remove devices without opening the computer case, making it useful for external hard disks and home network systems.

There have been experiments in using USB with monitors, but this offers few advantages over the current SVGA cables and so has not come into wide use. For similar reasons, USB has not completely replaced AT keyboard connections and PS/2 mouse connections.

USB has a bandwidth of 12 Mbps (12 million bits per second). However, in the real world, regular USB devices run at 1.5 Mbps and not many USB devices exceed 6 Mbps. USB 2.0 is on the horizon; it will support up to 480 Mbps.

See also: Firewire