 also elimi- nates the potential for electrical hazards. For example, when used in a building, fiber provides complete electrical isolation between a trans- mitter and a receiver. This means that the common ground between these two components that is required with the use of copper conduc- tors is eliminated. Another key advantage of optical fiber in many locations is the fact that you can route this type of fiber in ceilings or under floor panels without having to run the cable through a conduit. When this author first performed ceiling routing of optical fiber without using a conduit many years ago, the fire marshal appeared to have a high degree of anx- iety as the author explained to him that light, and not electricity, flowed through the cable. Now, in this more modern era, many build- ing codes have been revised to reflect the fact that optical fiber does not and cannot transport electricity. When complying with modern building codes, the ability to route fiber without the need for installing a conduit in the form of 200 to 300 ft of metal pipe can easily save sev- eral thousand dollars. Security If you watch spy movies you might recall one or more scenes when a person in a van parked outside of a fence around a high-security build- ing points an antenna toward the building, turns some dials, and watch- es a monitor that displays a message being typed by the occupant of the building. What the "spy" in the van is doing is operating a directional Introduction antenna that has sensitive electronics attached that receive electronic radiation emitted by electronic equipment inside the building. All electronic equipment and transmission systems radiate energy. By "reading" the radiated energy it becomes possible to note information being transmitted or received. Of course, what the movie may not show nor the story line tell is the fact that a spy using such a van in front of the CIA (U.S. Central Intelligence Agency) headquarters might be a bit noticeable, especially since the van contains a lot of electronics th