USB (Universal Serial Bus) is a platform independantly accepted standard, under Windows PCs as well as newer Apple Macintoshs. USB enhancement cards ae available for older PCs. These are plugged into available PCI slots.



USB is a serial bus, meaning that signals are transferred consecutively bit by bit, following the FIFO principle (First In, First Out). In contrast, older printers and scanners are connected to parallel ports. The parallel port always sends eight bits (one Byte) at once and is therefore faster than the serial port (COM1 und COM2).

Although the USB interface is serial as well, it sends data with a much higher throughput rate than the old serial COM interface and the parallel printer port (LPT1) and is therefore much faster. Moreover, the USB interface also transmits electricity in order to supply smaller devices with power (Low Power Class). High Power Class devices (e.g. monitors) need their own power supply or have to be connected to an USB-Hub with power supply.

Theoretically, 127 devices can be connected to the USB port, for example mouses, keyboards, printers, scanners, graph tablets etc.






USB Interface im deutschen Lexikon
USB Interface in het nederlandse encyclopedie