What device provides a magnetic heading and relies on a gyroscope?

The device that provides a magnetic heading and relies on a gyroscope is the Heading Indicator (HI). The Heading Indicator utilizes a gyroscopic mechanism to maintain a stable reference and displays the aircraft's heading in degrees, which is essential for navigation. The gyroscope helps the instrument maintain accurate directional information despite changes in the aircraft's orientation. This is particularly useful in maintaining consistent headings during flight.

While other indicators like the Horizontal Situational Indicator and Radio Magnetic Indicator also provide crucial navigational information, the HI specifically focuses on displaying the aircraft's heading based purely on a gyroscopic reference. The Transverse Mercator Indicator, on the other hand, does not serve this specific purpose in aviation navigation. The Heading Indicator is fundamental in ensuring pilots can navigate accurately, especially in poor visibility conditions where visual references are limited.