Which of the following inputs is required to indicate azimuth?

The correct answer is gyro signals because they provide critical information about orientation and heading in navigation systems. Gyro signals come from gyroscopes, which measure the rate of rotation and help determine the direction of movement relative to a fixed point, usually the Earth's surface. This data is essential for accurately indicating azimuth, which is the angle between a reference direction (often true north) and the line to a target.

In contrast, while synchronizers are important for maintaining timing and coherence in signals, they do not directly provide directional or azimuthal information. Resolvers can convert angular position or velocity into an electrical signal, but they are more commonly associated with feedback systems rather than direct azimuth measurements. Range rings are used in radar systems to indicate distance but do not help in determining azimuth. Therefore, gyro signals are essential for azimuth indication due to their direct relationship with the measurement of orientation and rotational motion.