Abstract :
Everywhere around us, information is being exchanged between two or more points. Several methods are commonly used to convey this information, including optical, RF, ultrasonic, and hardwired links. Anyone who has made use of one of these techniques will certainly remember its limitations: optical links operate only by line of sight, RF links are restricted by numerous regulations, ultrasonic links are interrupted by walls, and hardwired links require the costly installation of signal-carrying lines. Another alternative, a close relative of the hardwired link, is carrier current communication¿the exchange of data via pre-existing A.C. lines.
