Universal Serial Bus (USB) 2.0

Universal Serial Bus (USB) 2.0 is an external interface used on computers and other digital devices to transfer data through a cable. The designation “2.0” refers to the standard or version of the interface and it was released in 2000. While USB 3.0 was made standard in 2008, it is backward compatible with older versions. The primary difference between each version has been a major increase in transfer rates, with USB 2.0 improving upon the original release and 3.0 being even faster.

Major Features

USB is a plug-and-play interface, which means that a computer does not need to be powered off in order to plug in or unplug a component. For example, a media player can be connected to a computer via a USB while the machine is still in use, making these devices "hot swappable." The computer registers the device as another storage area and shows any files it contains. Other types of ports often require that someone shut down a computer before making such a connection, which led to much of the format's popularity.

The maximum approved length for a USB 2.0 cable is about 16 feet (5 meters). This limitation is based on how quickly a signal travels through the cable. If it takes too long, then the connected devices indicate that it was lost, and anything over about 16 feet (5 meters) exceeds this time.

Upgrade From 1.0

When USB standards change from an existing version to a newer version, as they did from 1.1 to USB 2.0, the major improvement is often the speed at which data transfers between connected devices. In 1.0 and 1.1, there were two speeds available: "low speed" with a rate of 1.5 megabits per second (Mbit/s) and "full speed" at 12 Mbit/s. USB 2.0 improved upon these with "hi-speed" transfer rates of 480 Mbit/s. Since this standard is typically backward compatible, the 2.0 version includes the older "full speed" and "low speed" rates to function with 1.0 devices.

Even in USB 2.0, "low speed" was often used for data transfers between a computer and a mouse or keyboard, except for high-end gaming devices. Memory sticks and external hard drives became much more powerful with the 2.0 standards, since they often ran into "bottlenecks" with older transfer rates. A bottleneck is a point at which data is slowed down by limitations in transfer rate, such as the slower speeds of 1.0 ports, even though the devices themselves can send and receive data much faster.

Common Devices

Aside from media players, many other external devices use these data ports, including digital cameras, mobile phones, and newer cable boxes. Native components also make use of this interface, such as mice, keyboards, and external hard drives, as well as printers and networking hardware. One of the most popular and convenient USB 2.0 gadgets is a memory stick, which can store data for easy transfer between machines.

Introduction of 3.0

In 2008, USB 3.0 was officially adopted as the new standard for this format. It introduced new connections that included more pins, allowing for "SuperSpeed" data transfer rates of up to 5 gigabits per second (Gbit/s). The 3.0 standard maintained backward compatibility, including "hi-speed" and "full speed" rates to function with older USB 2.0 devices.