HP Scanjet - Explanation of USB 2.0Explanation OF USB 2.0

The USB 2.0 specification is fully backward compatible with earlier versions of the specification (USB 1.0 and 1.1)and incorporates the higher performance fast data-transfer rate of 480 Mb/s.

By combining all three USB data transfer rates into the specification, peripherals already running at the slower speeds(1.5 Mb/s and 12 Mb/s) covered by earlier versions of the specification (1.0 and 1.1) are designed to be fullycompatible with other products designed to the USB 2.0 specification.

While all USB 2.0-compliant computer systems (laptops, notebooks, and desktops), must support all three data rates:1.5 Mb/s, 12 Mb/s, and 480 Mb/s, peripheral devices are a little less clear.

Peripherals may be available with the fastest data-transfer rate of 480 Mb/s, the slower data-transfer rate of 12 Mb/sor the lowest data-transfer rate of 1.5 Mb/s. Peripherals that support the fastest data transfer rate of 480 Mb/s arereferred to as USB 2.0 High Speed, and can use the High Speed logo given below.

Figure 1: USB Hi-speed symbol

Today, HP Digital Imaging has several Scanjet scanner products that are USB High Speed capable, including the HPScanjet 4500c series, HP Scanjet 4600 series, HP Scanjet 5500c series, and HP Scanjet 8200c series scanners.

Peripherals that support the slower 12 Mb/s data transfer rate can use the USB Certified logo given below, and aresometimes referred to as USB 2.0 Full-Speed devices.

Figure 2: USB symbol

This can cause some confusion because of the USB 2.0 reference. It is important to note that these devices are fullycompliant with the USB 2.0 specification for full-speed peripheral devices (12 Mb/s) which is essentially identical tothe USB 1.0/1.1 specification.

All other HP Scanjets, HP Digital Cameras, and HP Photosmart Printers connected by USB (as of the time of thiswriting) meet the 12 Mb/s specification.

Finally, USB peripherals that support that slowest 1.5 Mb/s data transfer rate, such as Keyboards, Mice, Joysticks,etc. are sometimes referred to as USB Low-Speed devices.

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