Universal Serial Bus
The Universal Serial Bus (short 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 the USB device chipsets can get very cheap compared to IEEE1394 chips providing the same functionality.
Specified by the USB Consortium, spec is publicly available on http:://www.usb.org/.
Different USB DVB Devices are available on the Market by different DVB Card Vendors, only High-Speed USB2.0 devices are able to transfer the full MPEG2 Transport Stream or high-datarate Transponders, Full-Speed are limited to a overall datarate (incl. Protocol overhead) of about 12MBit.
USB 1.1
The older Universal Serial Bus variant that specifies 1.5MBit (Low-Speed) and 12MBit (Full-Speed) Transfers. Used at Full-Speed by some USB DVB devices. The limitation to 12MBit forbids HDTV receiption and makes it impossible to receive some high-datarate services. The 480MBit USB2.0 variant overcomes these limitations.