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A remote reading compass is fitted with a free/slave switch. When slave is selected and the System is synchronized, the source of the heading that is displayed is:

  • A

    The magnetic compass.

  • B

    The gyroscopic unit.

  • C

    The flux detection unit.

  • D
    The deviation card.


A remote-reading compass system consists of a directional gyroscope and flux valve. The main direction indication of the system comes from a directional gyroscope, which is kept from drifting by tying it to the output of a flux valve unit for magnetic reference. This happens when “slave” is selected on the “free/slave” switch.

Alternative Explanation:

The Gyro-Magnetic Compass (GMC) system has two operational modes:

  • "SLAVE" mode: used when magnetic heading references are reliable. It is the normal magnetically-monitored mode. In this mode, the directional gyro is connected to the magnetic flux detector, which provides a stable magnetic reference to counteract the gyro's apparent drift.
  • "FREE" mode (Directional gyro): used when magnetic heading references are not reliable, such as in polar regions. In this mode, the system supplies an inertial heading reference, and the pilot manually introduces corrections to compensate for earth rate and other errors. If the switch is changed to "FREE," the magnetic signal from the flux valve is disconnected, the rotor/stator comparison stops, and the gyro is no longer tied to azimuth, and thus acts as a free gyro (DGI).

Note: Please read the question carefully as there are two similar questions in our database. One question pertains to FREE mode, while the other one pertains to SLAVE mode.

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