In a powerline network, computer data moves through a building's existing electric wiring. Each computer connects through a parallel port, a USB port, or an Ethernet port to a data adapter that plugs directly into an AC wall outlet. The same power transformer that feeds your house wiring also isolates your data network from your neighbors.
The most widely used standard for powerline networks is called HomePlug. The greatest advantage of HomePlug and other powerline networks is that the wires are already in place. Every AC wall socket in the house can double as a network connection point. It's also more secure than Wi-Fi, and it can reach greater distances than a Wi-Fi network with just one base station. Wi-Fi signals are often blocked by thick walls and other obstacles that make no difference to a powerline system.
Note
You must plug all your powerline adapters directly into wall outlets. Surge protectors and powerline conditioners often absorb powerline network data, because they see the data as "noise" on the AC power voltage. Conversely, if you're using a powerline network, you will want to connect your stereo or home theater system to power conditioners to filter out the noise produced by the network.
All equipment that follows the HomePlug specifications should work together in the same network. Some older types of powerline networking might also be available, but they're less reliable than HomePlug because they can suffer from interference caused by certain electrical appliances (such as vacuum cleaners and other appliances that use big motors or power transformers), and they don't always work well with very old house wiring. Today, it's better to stay away from anything that doesn't carry the HomePlug certification mark shown in Figure 2-4.
Figure 2-4. The HomePlug certification mark indicates that a powerline networking product has been approved by the HomePlug Powerline Alliance.
If installing Ethernet wiring is not practical in your building, a HomePlug network might be your best choice. When it works, which it does in most houses, it provides an easy, reliable network. But some would-be users report slow performance and other problems, so it's best to buy your HomePlug adapters from a retailer who will allow you to return them if they don't work in your house.