User Guide

Series III Avionics
Pilot's Guide
Page 35
DFS-43A Notes
1. The FREQUENCY SELECTOR knobs tune the DF-431B receiver directly. The display actually
shows the frequencies to which the receiver is tuned. In addition to rotation of the FREQUENCY
SELECTOR KNOBS, the receiver may be tuned by an external ARINC 429 digital bus.
2. Display intensity and panel lighting are controlled by external dimmer controls.
3. If the signal to which the receiver is tuned is lost for longer than 5 seconds, the electromechanical
display pointers will park at 90°.
4. The FREQUENCY SELECTOR KNOBS rotate continuously through all detents without end stops.
After the highest number is displayed, the next detent clockwise will cause the lowest number to be
displayed.
5. If the display is not functioning, the system frequency can be established as follows: Press the
transfer button for 7 seconds. The system will then be at 100 kHz. Rotating the large frequency
selector clockwise will increase the frequency in 100 kHz steps. Rotating the small knob clockwise
will increase the frequency in 1 kHz steps.
6. Frequencies selected between 100 kHz to 189 kHz and 1861 kHz to 1899 kHz are invalid and will
cause the display to blink off and on.