bi-directional light
71VHF omnidirectional range — This article is about the radio navigation aid. For other uses, see Vor. D VOR (Doppler VOR) ground station, co located with DME …
72People counter — A people counter is a device used to measure the number and direction of people traversing a certain passage or entrance per time unit. The resolution of the measurement is entirely dependent on the sophistication of the technology employed. The… …
73Oscar/Technische Verdienste — Der Oscar für technische Verdienste (Academy Technical Achievement Award) ist eine seit 1931 vergebenene Auszeichnung der Academy of Motion Picture Arts and Sciences und würdigt herausragende Leistungen auf dem Gebiet der Verbesserung technischer …
74USB — This article is about the computer bus to connect peripherals. For other uses of USB, see USB (disambiguation). Universal Serial Bus Original logo Type Computer Hardware Bus …
75Optical amplifier — An optical amplifier is a device that amplifies an optical signal directly, without the need to first convert it to an electrical signal. An optical amplifier may be thought of as a laser without an optical cavity, or one in which feedback from… …
76Right- and left-hand traffic —   countries with right hand traffic …
77Fermi paradox — The Fermi paradox is the apparent contradiction between high estimates of the probability of the existence of extraterrestrial civilizations and the lack of evidence for, or contact with, such civilizations.The extreme age of the universe and its …
78Radar — For other uses, see Radar (disambiguation). A long range radar antenna, known as ALTAIR, used to detect and track space objects in conjunction with ABM testing at the Ronald Reagan Test Site on Kwajalein Atoll …
79Double track — This article is about the use of two tracks on a railway line. For the sound recording technique, see doubletracking. A double track railway line A double track railway usually involves running one track in each direction, compared to a single… …
80History of radar — The history of radar starts with experiments by Heinrich Hertz in the late 19th century that showed that radio waves were reflected by metallic objects. This possibility was suggested in James Clerk Maxwell s seminal work on electromagnetism.… …
