The PLC is a network technology, using the electrical infrastructure of the house (electrical outlets), to transmit information between different hosts (typically computers and router). It is a competing technology of WLAN, and uses microwaves for data transmission . This technology is normally used by electric operators to get maintenance information about the network.
The CPL allows better data transmission than WiFi. The scope is generally better, and risks of piracy are reduced because the waves are supposed to stop after the meter readers.
Using a PLC?
The PLC can be used in all homes. However, you understand a few concepts of electricity.
The PLC technology is employed between a power phase, and neutral. If you have a three-phase installation at home (4 poles), then you can have 3 separate PCL networks, depending on which phases are connected your equipment. The equipment can therefore normally not communicate from one network to another without specific equipment. You should check the wiring diagram of your facility to know the phase used in each room.
It is possible to combine these networks using a coupler stage, which repeat the signal of the PCL on each phase.
You can also build your own phase coupler. It consists of high pass filters between phases: from simple capacitors! (they block the low frequency power, and allowing only the high frequency of the PLC).
/!\ Warning /!\ Tweaking the electrical board can be hazardous (electrification, electrocution, fire), it is strongly advised to call for a professional!
Introduction to power line communications (PLC)
Architecture of powerline communication (PLC) devices
Some people prefer to say that Wi-Fi sends microwave and not the CPL. The PLC uses the electrical grid, which is not isolated electro-magnetically. The cables therefore act as an antennae. The technology has potentially the same risks as WiFi. To reduce risk, use an Ethernet network with shielded cables.
Original tip by Nabla's from French version of this site.