themesfor.blogg.se - Usb ports powered when computer is off

As you'll see on the next page, the USB standard allows for devices to draw their power from their USB connection. By chaining hubs together, you can build up dozens of available USB ports on a single computer. You plug the hub into your computer, and then plug your devices (or other hubs) into the hub. A sample list of USB devices that you can buy today includes:Ī typical USB four-port hub accepts 4 "A" connections.Ī hub typically has four new ports, but may have many more. Just about every peripheral made now comes in a USB version. The Universal Serial Bus gives you a single, standardized, easy-to-use way to connect up to 127 devices to a computer. The goal of USB is to end all of these headaches. Unfortunately, the number of card slots is limited and some of the cards are difficult to install.

Devices that needed faster connections came with their own cards, which had to fit in a card slot inside the computer's case.

Most computers had at most two serial ports, and they were very slow in most cases.

Modems used the serial port, but so did some printers and a variety of odd things like personal digital assistants (PDAs) and digital cameras.Things like external storage media, which need a high-speed connection into the computer, would use the parallel port as well, often with limited success and not much speed. Printers connected to parallel printer ports, and most computers only came with one.