Wednesday, March 30, 2011

USB Cables and Connectors

Connecting a USB device to a computer is simple,we can find the USB connector on the back of your machine and plug the USB connector into it.










The rectangular socket is a typical USB socket on the back of a PC.

If it is a new device, the operating system auto-detects it and asks for the driver disk. If the device has already been installed, the computer activates it and starts talking to it. USB devices can be connected and disconnected at any time.


A typical USB connector, called an "A" connection


A typical USB four-port hub accepts 4 "A" connections.

A hub typically has four new ports, but may have many more. You plug the hub into your computer, and then plug your devices (or other hubs) into the hub. By chaining hubs together, you can build up dozens of available USB ports on a single computer.

Hubs can be powered or unpowered. As you will see on the next page, the USB standard allows for devices to draw their power from their USB connection. Obviously, a high-power device like a printer or scanner will have its own power supply, but low-power devices like mice and digital cameras get their power from the bus in order to simplify them. The power (up to 500 milliamps at 5 volts) comes from the computer. If you have lots of self-powered devices (like printers and scanners), then your hub does not need to be powered -- none of the devices connecting to the hub needs additional power, so the computer can handle it. If you have lots of unpowered devices like mice and cameras, you probably need a powered hub. The hub has its own transformer and it supplies power to the bus so that the devices do not overload the computer's supply.

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