with north-seeking action by other than magnetic means, e.g. gyrocompasses using earth's rotation

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Gyroscopes; Turn-sensitive devices using vibrating masses; Turn-sensitive devices without moving masses; Measuring angular rate using gyroscopic effects > Rotary gyroscopes > for indicating a direction in the horizontal plane, e.g. directional gyroscopes > with north-seeking action by other than magnetic means, e.g. gyrocompasses using earth's rotation