polarity indicator
41Test and tagging — is a generic name given to the process of visually inspecting and electrically testing in service electrical equipment for personal use and/or safety. Colloquially, it is also referred to as; tagging, test tag, test and tag, electrical tagging,… …
42Digital video testing — in broadcast video, for example, is the process of validating and verifying that the video content and other data is being correctly processed, stored and transported. Despite the fact that the data is digital, most digital tv (DTV) system… …
43Acid — This article is about acids in chemistry. For the drug, see Lysergic acid diethylamide. For other uses, see Acid (disambiguation). Acidity redirects here. For the novelette, see Acidity (Novelette). Acids and Bases …
44Earth Sciences — ▪ 2009 Introduction Geology and Geochemistry The theme of the 33rd International Geological Congress, which was held in Norway in August 2008, was “Earth System Science: Foundation for Sustainable Development.” It was attended by nearly… …
45Nickel–metal hydride battery — NiMH redirects here. For other uses, see NIMH (disambiguation). Nickel–metal hydride battery Modern, high capacity NiMH rechargeable cells specific energy 60–120 W·h/kg[1] …
46Current loop — This article is about the electrical signaling schemes. For the oceanic phenomenon, see Loop current. A current loop describes two different electrical signalling schemes. Contents 1 Digital 2 Analog 3 Process control use …
47NEMA connector — Twist lock connector redirects here. For the device used in intermodal shipping, see Twistlock. Ungrounded and grounded power plugs …
48Oscilloscope history — This article discusses the history and gradual development of the Oscilloscope. Contents 1 Hand drawn oscillograms 2 Automatic paper drawn oscillograph 3 Photographic oscillograph 4 …
49List of philosophy topics (I-Q) — II and thou I Ching I Ching I proposition I Thou I Thou relationshipIaIamblichus (philosopher)IbYahya Ibn Adi Yahya Ibn Adi Ibn al Arabi Muhyi al Din Ibn al Arabi Abu Bakr Ibn Bajja Abu Bakr Ibn Bājja Abu Bakr Muhammad Ibn Yahya Ibn as Say igh… …
50Silica gel — Identifiers CAS number 63231 67 4  …
