Scientific Instruments & Appliances commutator is an instrument to change of reverse the direction of an electric current. in dynamo used to convert the alternating current into direct current.
Scientific Instruments & Appliances computer is a technical device designed to find instantaneous solutions of huge and complex calculation based on the information already fed.
Scientific Instruments & Appliances mariner's compass is an apparatus for determining direction, graduated to indicate 33 directions. the "n" point on the dial indicates north pole and the "s" point, south pole.