Magnetic Compass Modules: How are they used?

I can't think of anywhere that a magnetic compass is ever used in communications.

Are you referring to the actual use of a compass or the effect that things like the coil in a speaker has on a compass? If you are that's a completely different thing and is called electromagnetism and that crops up in many places.

When a pilot radios the tower on what his heading is?

When a pilot refers to his heading he doesn't actually use a magnetic compass. The primary instrument for direction indication is the DG or Directional Gyroscope or gyrocompass not a magnetic compass.

This system consists of a gyroscope that is mounted in a gimbal and aligned with true north not magnetic north. As the aircraft moves and turns the gyroscope is free to turn so it will always point to true north. The only time the magnetic compass is used is when the DG is initially powered up and aligned with true north but even then a correction needs to be applied to convert the magnetic north of the compass into true north.

Over recent years however the GPS (Global Positioning System) has been making more inroads into aircraft instruments but aircraft are still required to have DG as a backup instrument.

Hi,

magnetic compasses can be combined with GPS-modules in order to have the exact direction of the device even without movement.

Look on "dreifach-einfach.de" and find a new electronic touristic guide using that combination.
Regards Uwe