This is the largest area of application of biometric technologies, and the most direct lineage to the feudal gate keeping system. Initially mainly used in military and other "high security" territories, physical access control by biometric technology is spreading into a much wider field of application. Biometric access control technologies are already being used in schools, supermarkets, hospitals and commercial centres, where the are used to manage the flow of personnel.
Biometric technologies are also used to control access to political territory, as in immigration (airports, Mexico-USA border crossing). In this case, they can be coupled with camera surveillance systems and artificial intelligence in order to identify potential suspects at unmanned border crossings. Examples of such uses in remote video inspection systems can be found at
A gate keeping system for airports relying on digital fingerprint and hand geometry is described at
An electronic reconstruction of feudal gate keeping capable of singling out high-risk travellers from the rest is already applied at various border crossing points in the USA. "All enrolees are compared against national lookout databases on a daily basis to ensure that individuals remain low risk". As a side benefit, the economy of time generated by the inspection system has meant that "drug seizures ... have increased since Inspectors are able to spend more time evaluating higher risk vehicles".
However, biometric access control can not only prevent people from gaining access on to a territory or building, they can also prevent them from getting out of buildings, as in the
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This book gives a fascinating glimpse of the many documented attempts throughout history to develop effective means for long distance communications. Large-scale communication networks are not a twentieth-century phenomenon. The oldest attempts date back to millennia before Christ and include ingenious uses of homing pigeons, mirrors, flags, torches, and beacons. The first true nationwide data networks, however, were being built almost two hundred years ago. At the turn of the 18th century, well before the electromagnetic telegraph was invented, many countries in Europe already had fully operational data communications systems with altogether close to one thousand network stations. The book shows how the so-called information revolution started in 1794, with the design and construction of the first true telegraph network in France, Chappe's fixed optical network.
http://www.it.kth.se/docs/early_net/