While observation provides sound security, it is less acceptable to many people. Until recently, it was not a serious option because it was technically difficult, if not impossible, and too expensive to justify. The proliferation of inexpensive computers, however, and, more recently, digital cameras and monitors have made it easier for owners to watch critical areas, such as safes and bank lobbies. Now it is a fairly simple matter to watch nearly every corner of a building and, at the same time, witness every action of every employee or visitor. Observation is great for security, but not so good for people's privacy.
Cameras are only one used surveillance tool, however.
Another, less obtrusive method, is electronic visitor registration. When a visitor enters a building, the receptionist enters information by keyboard, for the apparent purpose of printing an identification badge. At the same time, the visitor's authorization is transmitted to security points, notifying others of the visitor's identity and purpose. Special paper can be used for the identification badge, which, after a fixed time, changes color, thereby making it useless later. Badges with microchips can be used to carry information, too.