(under subclass 300) Device comprising means influenced by an external magnetic field, usually that of the earth, and either (1) indicating a direction or deviation from a direction, related to that of the field or (2) controlling a telemetering system to an indicator of such direction or deviation.
SEE OR SEARCH THIS CLASS, SUBCLASS:
310, for a magnetic compass supported on a pendulum for use in a borehole.
313, for means indicating inclination and direction, usually magnetic, of a borehole.
316+, for a gyromagnetic compass.
319, for a gyroscopically stabilized magnetic compass. 352, for a magnetic compass combined with a different directional indicator.
SEE OR SEARCH CLASS
324, Electricity: Measuring and Testing,
259, for testing a magnetic field by using a permanent magnet (e.g., compass needle).
335, Electricity: Magnetically Operated Switches, Magnets, and Electromagnets,
302+, for permanent magnets of a particular structure or material.
