“Powerline Communications” (PLC) is the name given to the technology which passes information (as an ADSL signal) from narrow band to broadband over an electrical circuit. This cabled electrical network may be in a house or a flat, for example. PLC works by superimposing a modulated signal at a higher frequency than the 50 Hertz electrical current delivered by your energy supplier to power your domestic electrical equipment.

Depending on the language, Powerline Communications may be known by two different abbreviations:

• PLC (Powerline Communications)
or
• CPL (Courants porteurs en ligne)

PLC technology has existed for a long time, but only narrow band was in use for remote control applications (public street lighting) and home automation (intercom/entry phones). Broadband PLC did not appear until the end of the 1990’s:

• 1950: public street lighting operations, remote control relays.
Around 1985: research started on using the electrical distribution network as a means of transmitting data.
• 1996: the first signal transmission tests carried out using an electrical network.
• 2000: the first French experiments carried out by EDF R&D.
• 2005: the ISPs (Internet Service Providers) begin to offer PLC instead of WiFi for television signal broadcasts over the Internet via a modem and a decoder placed by the television set.
• 2006: in September 2006, PLC is now available at 200Mb which enables users to receive high definition television in every room in the house.

With PLC technology, it is possible to transfer computer data via the electrical supply network. This means that you can create or extend an existing network and share Internet access when you use LEA’s CPL “NetPlug” connectors. The principle underlying PLC consists of superimposing a higher frequency (but weaker strength) signal over the existing 50Hz electrical signal.

This second signal is transmitted over the electrical installation and can be received and decoded remotely. This means that the signal emitted by the first LEA “NetPlug” can be received by all the other LEA “NetPlugs” connected to the same electrical network. An integrated coupler in each of the LEA “NetPlugs” eliminates the low frequency component before processing the signal.

In practice, there are very few constraints:

• In theory the maximum distance for establishing communication between two NetPlugs is 300 meters (in practice this is 200 meters, which is considerably larger  than a WiFi access in a closed environment).

• Three phase electrical installations (consisting of a 380 volt supply from your energy company, which is then divided into three 220 volt phases) do pose a problem. Because the three phases are side by side when they exit the meter, the natural phenomenon of induction means that coupling of the phases may occur (although data flow should not be greatly affected). However, there is a simple solution for this problem – a phase coupler can be installed (either active or passive depending on requirements).

The domestic electricity meter and circuit breakers act as natural filters which prevent the signal from being broadcast outside the home. However, although the electricity meter acts as a natural filter for high frequency PLC, it is still possible to have encryption on your PLC network. This is due to the fact that each NetPlug has an integrated DES56 bits electronic encryption which is activated by default with a generic encryption key.
SoftPlug software (which can be downloaded from this website) allows you to create and administer PLC networks in the following way:
The NetPlugs installed on the electrical network are detected by the software via the locally connected NetPlug (i.e. the one connected to the computer on which SoftPlug software has been installed). Once the NetPlugs have been detected, it is then possible to create one or several networks, to allocate a name to each network and then use that network or particular NetPlug.
The difference between PLC and WiFi system is that a NetPlug on one network cannot “sniff” data forwarded between NetPlugs on another network. This gives total security.

PLC and WiFi are complementary. It is for this reason that LEA has developed the NetPlug WiFi Turbo g. This product means that when you need mobility, it will let you pick up your Internet signal from your PLC network and then broadcast it to the room of your choice, or even to the bottom of your garden…