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Some more details found on a site
The USB, a universal serial port
The universal serial port, USB (Universal Serial Bus), is intended for low-speed devices. You can connect up to 127 devices together in a Plug and Play manner, without needing to configure anything... And this can be done both hot and cold, with the necessary resources being allocated on the fly by the operating system. The first drivers appear (notably in version 3 of Microsoft DirectX) and most motherboards today are capable of supporting this type of device. For proper operation, it is also necessary for USB devices to be recognized by the machine's BIOS... However, this point is problematic because most current BIOSes are unable to do so. Therefore, plugging in a USB keyboard doesn't bring anything today since there's a great chance it won't be recognized and won't function.
The USB versions 1.0 and 1.1 are primarily intended for devices that do not require high data rates (i.e. a maximum of 1.5 MB per second = 12 Mbits/s), the USB port was born from an agreement among members of a consortium including Digital, Compaq, IBM, Intel, Microsoft, and NEC. But many other manufacturers have already joined this cause. For example, Canon has announced a generation of inkjet printers incorporating USB technology, along with Cherry and Keytronic (for keyboards), as well as Philips (in terms of monitors). And this list is far from exhaustive...
USB version 2.0 boosts the bitrate up to 480 Mbits/s or 60 MB/s
Indeed, the USB port is capable of supporting keyboards, joysticks, mice, modems, speakers, scanners, printers, and even phones. In this latter case, the central units of our machines, connected to phones via the USB port, simply turn into telephone exchanges. One conceivable application of these new possibilities would be, for instance, managing contacts and recording voice messages, receiving faxes or customized files.
Finally, to facilitate the installation of certain extensions in the chain, hubs are installed in screens, printers, keyboards, or simply in standalone versions. And for even more flexible use, the USB port supplies electricity to the connected devices. Thus, there's no need to clutter the desk with external power supplies and transformers. It naturally becomes the ideal bus for laptops. What a space saver! Lastly, a final detail, the maximum length of a USB cable, without resorting to a hub, is five meters.
Another possible use of the USB port is to retrieve images from digital cameras. No need for specific docks or to restart the machine. The camera easily connects to the central unit and is automatically recognized by the system. All that remains is to transfer the contents of the device to the PC... But all this remains theoretical because, in practice, some major problems arise. Thus, a portion of the bandwidth is allocated to each new device on the bus, there comes a point where it saturates. And well before the 127th device! At this point, don’t expect to connect anything else to the bus. The newcomer would not be recognized.
Today, there are many adapters to convert USB to:
- Serial ports.
- Parallel ports.
- Video ports.
- Network port in RJ45 10Base-T or 100Base-TX.
Some more details found on a site
The USB, a universal serial port
The universal serial port, USB (Universal Serial Bus), is intended for low-speed devices. You can connect up to 127 devices together in a Plug and Play manner, without needing to configure anything... And this can be done both hot and cold, with the necessary resources being allocated on the fly by the operating system. The first drivers appear (notably in version 3 of Microsoft DirectX) and most motherboards today are capable of supporting this type of device. For proper operation, it is also necessary for USB devices to be recognized by the machine's BIOS... However, this point is problematic because most current BIOSes are unable to do so. Therefore, plugging in a USB keyboard doesn't bring anything today since there's a great chance it won't be recognized and won't function.
The USB versions 1.0 and 1.1 are primarily intended for devices that do not require high data rates (i.e. a maximum of 1.5 MB per second = 12 Mbits/s), the USB port was born from an agreement among members of a consortium including Digital, Compaq, IBM, Intel, Microsoft, and NEC. But many other manufacturers have already joined this cause. For example, Canon has announced a generation of inkjet printers incorporating USB technology, along with Cherry and Keytronic (for keyboards), as well as Philips (in terms of monitors). And this list is far from exhaustive...
USB version 2.0 boosts the bitrate up to 480 Mbits/s or 60 MB/s
Indeed, the USB port is capable of supporting keyboards, joysticks, mice, modems, speakers, scanners, printers, and even phones. In this latter case, the central units of our machines, connected to phones via the USB port, simply turn into telephone exchanges. One conceivable application of these new possibilities would be, for instance, managing contacts and recording voice messages, receiving faxes or customized files.
Finally, to facilitate the installation of certain extensions in the chain, hubs are installed in screens, printers, keyboards, or simply in standalone versions. And for even more flexible use, the USB port supplies electricity to the connected devices. Thus, there's no need to clutter the desk with external power supplies and transformers. It naturally becomes the ideal bus for laptops. What a space saver! Lastly, a final detail, the maximum length of a USB cable, without resorting to a hub, is five meters.
Another possible use of the USB port is to retrieve images from digital cameras. No need for specific docks or to restart the machine. The camera easily connects to the central unit and is automatically recognized by the system. All that remains is to transfer the contents of the device to the PC... But all this remains theoretical because, in practice, some major problems arise. Thus, a portion of the bandwidth is allocated to each new device on the bus, there comes a point where it saturates. And well before the 127th device! At this point, don’t expect to connect anything else to the bus. The newcomer would not be recognized.
Today, there are many adapters to convert USB to:
- Serial ports.
- Parallel ports.
- Video ports.
- Network port in RJ45 10Base-T or 100Base-TX.
