at require a significant amount of power. In addition, it is rather difficult to hide the directional antenna on top of the vehicle. The electronic emissions are referred to in the spy (espionage) com- munity as tempest. To make a building or another site "tempestproof," the site is hardened by lead shielding. When copper cable is used to con- nect buildings, these cables, too, must be shielded. In comparison, an optical fiber does not radiate energy and thus does not require shielding. Another benefit of optical fiber with respect to security is the fact that, unlike the tapping of a copper circuit, which could be unnotice- able, tapping an optical fiber requires the insertion of an optical splitter. This insertion results first in a loss of signal and then in a loss of signal strength. Thus, it is easier, with applicable equipment, to note a tap of an optical signal than an electrical signal. In light of the preceding observa- tions, you might make a reasonable guess as to the type of cable favored for use by intelligence agencies to interconnect buildings. Weight and Size The glass on plastic used in an optical fiber cable is a thin strand of material. Even when fiber-optic cable is surrounded by a jacket for pro- tection, the weight and diameter of the resulting cable are considerably less per meter than those of copper cables, which provide only a fraction of the transmission capacity of optical fiber. Disadvantages of Optical Fiber Although we noted a considerable number of advantages associated with the use of an optical transmission system, we should also note Chapter One some of the limitations associated with the use of this type of transmis- sion system. Two of the key limitations associated with the use of opti- cal fibers are cable splicing and the cost of optical fiber. Cable Splicing When you need to extend a copper cable within a building, it is possi- ble to simply strip the insulators on the pair to be extended and strip another wire pair, twist the wire strips for each pair together, and bond t