Abstract: A two-axis platform comprises an azimuth gimbal rotatable about an azimuth axis. In the azimuth gimbal an inner gimbal is mounted about an axis. A two-axis gyro having input axes and a spin axis is located in the inner gimbal. The spin axis is always maintained horizontal by a torquer which is controlled by a level sensor. By the horizontal component of the rotary speed of the earth, which acts on the input axis of the gyro, the spin axis is rotated into North through the torquer. The azimuth angle of the spin axis is measured in a first position for elimination of the influence of gyro drifts including axial mass unbalance. Then, azimuth gimbal and inner gimbal are simultaneously rotated by 180.degree. about their axes. Subsequently, the azimuth angle is measured again, to which the spin axis is adjusted. The middle between these positions provides a North indication compensated for gyro drifts.

Abstract: An automatic trim control system designed to be used on power boats equipped with electric or hydraulic actuated trim tabs is disclosed. The unit senses out of trim conditions in two planes (pitch and roll) and transmits control signals to the electro-mechanical control lines to reposition the trim tab attitudes, thereby reestablishing preset trim conditions as required.

Abstract: In order to correct errors in the reading of a graduated scale, especially on a compass card driven by a damped gyroscopic system, the scale is juxtaposed with a block having slits simultaneously alignable with different scale graduations and illuminable by respective light sources within the block. The light sources can be selectively energized by a rotary switch whose bank contacts are connectable via a changeover switch to either of two groups of light sources for positive or negative deviations from a reference position; the slit so illuminated serves as a pointer by coacting with a confronting scale graduation.

Abstract: An all solid state gyromagnetic compass system operable in the slaved, compass and free gyro modes wherein magnetic compass error rates, fast or slow slaving rates, gyro drift rates, earth's rate and set heading rates are all produced by means of a solid state analog angle rate generator. This generator includes a dual slope integrator responsive to scaled d.c. voltages representing the required rates and which generate shaped sine and cosine control signals therefrom for the various system modes having constant amplitudes and variable frequency representing the required rates. The system outputs are provided in standard three wire synchro format for interfacing with any utilization system requiring conventional slaved gyromagnetic compass data, magnetic compass data or free gyro data.