USB (Universal Serial Bus) Interface

USB is a popular interface for external hard drives. USB 1.0, the first USB standard, was not fast enough to be used with hard drives so it was not used until later when USB 1.1 and 2.0 were introduced. Practically every PC has at least two USB ports. USB 2.0 has a transfer rate up to 57 MB/s and can be used to connect up to 127 devices to a PC. Many devices use the USB interface, including printers, keyboards, mice, modems, digital cameras, scanners and flash drives.

USB Connectors

The USB standard uses two types of connectors known as "A" and "B". The rectangular "A" connector is used for upstream and the square "B" connector for downstream. Due to the different shapes of the "A" and "B" connector, it is impossible to incorrectly attach a USB device to a PC.