Radio altimeter

1. DH light.
Flashes together with the DH light on the ADI when the indicated altitude is less than the setting of the DH index.
2. DH index.
Indicates the height at or below which the DH light will illuminate.
3. DH set knob.
Sets the DH index. The setting will only affect the DH lights associated with the particular indicator.
4. Test button.
When depressed, the indicator shall read 100+/-5 feet and the warning flag shall appear. The radio height bar on the ADI will be out of view.