An astronomical telescope mounted in the meridian and turning on a fixed east-and-west axis.

plural of transit instrument

plural of block instrument

(rail transport, UK) An instrument installed in a cabinet, used in block signalling installations.

(aviation) An airline selected by government to represent the country.

plural of chosen instrument

plural of instrument approach

Maker of scientific instruments. / Maker of musical instruments.

plural of flight instrument

(aviation, usually in the plural) A device that measures and displays data concerning one or more aspects of the situation of an aircraft, such as its altitude, attitude, airspeed, etc.