Radio altimeter.

RADIO ALTITUDE INDICATOR.

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.