Today, 17:57
Don't confuse those old gyro compasses to an RMI. The old gyrosyn compass was a fixed background with a needle pointing to the airplane magnetic heading. The needle was driven by what was known as a flux gate - a measurement of the magnetic field that was processed through a gyro stabilizing routine to avoid compass errors caused in turning, climbing accel / decel as seen in a wet compass.
Later, RMIs were developed, wherein the background card driven by the flux gate moved to indicate magnetic heading under the 12 o'clock index (thereby eliminating the need for the needle), and included 1 or 2 needles that were driven by VOR, TACAN and /or ADF receivers to indicate the magnetic bearing to a station. If no station was received, the associated needle was typically set to indicate 180...