Each FCC uses radio altitude from its on-side RA receiver/ transmitter. The FCCs use radio altitude in the approach control and low altitude flight calculations.
The autothrottle uses radio altitude in the TO/GA calculations and autothrottle flare calculations.
The DEUs use radio altitude data to calculate the type of radio altitude display and the radio altitude value to show on the display units.
The weather radar R/T uses radio altitude to turn on or off the predictive windshear function and to enable/disable display and alert functions.
The GPWC uses radio altitude in its ground proximity alert and warning logic calculations.
The FDAU records radio altitude values.
The TCAS computer uses radio altitude to set the sensitivity levels for intruder advisory calculations and to find if an intruder aircraft is on the ground.