Universal Serial Bus

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The Universal Serial Bus (USB) is a serial 4-wire bus (GND, Power and a differential Data Signal transferred over 2 wires). A quite clever designed protocol for communication between the PC Host and peripheral devices like e.g. DVB Receivers. Since devices are defined as dumb clients that get polled by the USB Host Controller, USB device chipsets can be very cheap compared to IEEE1394 chips that provide essentially the same functionality.

Specified by the USB Consortium, spec is publicly available on http:://www.usb.org/.

Many USB DVB devices are available from an wide assortment of different vendors,

USB 1.1

The older Universal Serial Bus variant that specifies data transfer rates of 1.5 Mbps (Low-Speed devices) and 12 Mbps (Full-Speed devices).

Used at Full-Speed by some USB DVB devices. Because Full-Speed devices are limited to a overall datarate (incl. Protocol overhead) of about 12Mbps, this essentially prevents the reception of HDTV steams and makes it impossible to receive some high-datarate services. Only High-Speed USB2.0 devices are able to transfer the full MPEG2 Transport Stream or high-datarate Transponders.

USB 2.0

In terms of reception of digital TV services, the 480Mbps transfer rate of USB 2.0 overcomes several of the limitations of earlier USB 1.1 devices.

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