What’s a Port Expander?

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A port expander allows one computer port to connect to multiple devices. There are internal and external expanders, also known as splitters. They are commonly used in homes for power, cable, and A/B switching. Expanders are made for various ports, with USB and Ethernet being the most common. Commercial systems have specialized expanders for different power and load requirements.

A port expander is a device that allows one port on a computer to connect to multiple devices. There are two basic forms of port expansion: internal and external. An internal expander has a connection inside the computer, usually on the motherboard, and the only part the user sees is the expansion plate containing multiple ports. An external device connects to the existing port and therefore has multiple connection points. When not part of a computer system, these devices are commonly known as splitters.

In the non-IT world, splitters are very common. Extension cords and power strips are present in almost every modern home. Both of these devices will split a single outlet across multiple devices. Cable splitters are also in many homes, allowing a single coaxial cable to provide cable television to multiple sets. Some systems may even use an A/B box, a device that connects multiple sets of devices to the same system, but switches between them when switching between A or B mode.

These devices all perform the same basic job as a port expander. The expander will connect to a single point, but will have multiple connections for devices. They go by different names, like switches, hubs, or splitters, but they all do the same thing. Expanders are made for almost any type of port, but the most common home versions are for universal serial bus (USB) and Ethernet.

An internal port expansion is common on desktop systems. A single expansion plate will have multiple ports, often several USBs. Inside the computer, the ports are all part of a single card that will plug into a designated spot on the motherboard. The motherboard spot is programmed to handle a single port, but the card that connects to the external ports handles the routing so the system isn’t overloaded.

An external port expander is usually much more obvious. One cable will run from the computer to a secondary box. That box will have several spots identical to the one on the main system. For example, an Ethernet hub connects to the network port on a computer and then splits the connection in many different ways. This will allow multiple network devices to share the same port.
On commercial systems, there are a large number of different types of port expanders. Servers often have very different power and load requirements than standard user systems. They will commonly use an external device to route and monitor usage through the various ports. These systems range from those similar to a home system up to specialized internal hardware built to connect to external expansions.

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