What is a USB Hub?

A USB hub can be used to provide direct communication between a number of USB-enabled devices, or more commonly to extend the capabilities of a single USB port of a computer and allow multiple devices to use a single connection. This can be useful when a computer is a lack of USB ports and mouse, keyboard and printer can be connected via a USB hub. USB (Universal Serial Bus) was built around 1996, with 1.5Mbps and 12Mbps rate defined data. The model was designated as 1.5Mbps low speed, while the standard was described as 12 Mbps full speed. Version 1.1 was very popular and many devices, such as computers and printers soon adopted this standard. Finally, in 2008, the USB 3.0 specification was completed and the data rate of potential increased to a huge 5Gbs while ensuring compatibility with the USB 2.0 standard.

A USB Hub typically have only one upstream port for connecting a PC to a hub or even another PC, whereas the downstream ports are used to connect a range of peripherals to a PC. Indeed, you build a network of devices that can access a single PC, with 127 ports and the maximum number of ports allowed on a USB network.

PC makers have rapidly adopted the rules it has simplified the way devices can be connected to a single PC. Printers are no longer required to connect to a PC via a complicated parallel cable and mouse, keyboard and external devices such as CD players, DVD players and Flash all could use simple USB connection to the PC.

There are practical limits on the maximum length of cable to be used with USB specifications, with 3 meters being proposed for USB 1.1 and 3.0 and 5 meters for USB 2.0 specification.

USB hubs are often fueled by a power source but a bus-powered hub is powered from a host computer via the same cable. The maximum power that can be drawn from a host device is 500mA so a bus-powered hub so it can only support 4 ports downstream as the hub requires is 100mA, 100mA leaving for each device downstream. A hub that is powered from a power supply can provide the power of 500mA for each single connected device. If you use a hub port 7, for example, and you have a power problem, check the ratings of the connected devices, although you should rarely find that your devices are collectively draw too much power. Some vendors are manufacturing hubs with greater power in response to the request.

A USB hub downstream ports typically require a type A-flat connector as built-in ports for a PC. Cables with connectors on one type will carry the power of the connected device, and data. However a type B connector is almost square in shape and is used to connect the upstream port hub, and take power and data, although in some cases, being used as a power cable to pull the power your upstream host. So if you have a lack of USB ports on your PC, consider a USB Hub, low-cost devices that are often compact plug & play, so there is no technical knowledge needed to create one.