Like phone companies, power companies also have lines strung all over the world. The difference is that they have power lines in a lot more places than phone companies have fiber optics. This makes power lines an obvious vehicle for providing Internet to places where fiber optics haven't reached.
These power lines are just one component of electric companies' power grids. In addition to lines, power grids use generators, substations, transformers and other distributors that carry electricity from the power plant all the way to a plug in the wall. When power leaves the power plant, it hits a transmission substation and is then distributed to high-voltage transmission lines. When transmitting broadband, these high-voltage lines are the first obstacle.
The power flowing down high-voltage lines is between 155,000 to 765,000 volts. That amount of power is unsuitable for data transmission. It's too "noisy."
As stated before, both electricity and the RF used to transmit data vibrate at certain frequencies. In order for data to transmit cleanly from point to point, it must have a dedicated band of the radio spectrum at which to vibrate without interference from other sources.
Hundreds of thousands of volts of electricity don't vibrate at a consistent frequency. That amount of power jumps all over the spectrum. As it spikes and hums along, it creates all kinds of interference. If it spikes at a frequency that is the same as the RF used to transmit data, then it will cancel out that signal and the data transmission will be dropped or damaged en route.
BPL bypasses this problem by avoiding high-voltage power lines all together. The system drops the data off of traditional fiber-optic lines downstream, onto the much more manageable 7,200 volts of medium-voltage power lines.
BPL Retailers
For a complete list of third party products that support BPL, see HomePlug-certified Products.
Once dropped on the medium-voltage lines, the data can only travel so far before it degrades. To counter this, special devices are installed on the lines to act as repeaters. The repeaters take in the data and repeat it in a new transmission, amplifying it for the next leg of the journey.
In Current Communications Group's model of BPL, two other devices ride power poles to distribute Internet traffic. The CT Coupler allows the data on the line to bypass transformers.
The transformer's job is to reduce the 7,200 volts down to the 240-volt standard that makes up normal household electrical service. There is no way for low-power data signals to pass through a transformer, so you need a coupler to provide a data path around the transformer. With the coupler, data can move easily from the 7,200-volt line to the 240-volt line and into the house without any degradation.
In the next section, we will see how the data moves around once it reaches the house.
