The RCFA Telemetry System can be used as a variometer. The altitude data is provided by GPS module or barometer (if present). Barometer altitude is in general much better quality but some GPS modules as u-Blox M8 or M7 series can provide very good 3D positioning signal as well. Telemetry system allows Pilot to control ascending and descending in real time from the ground. Certain sound patterns in the receiver are used to indicate altitude changes.
The variometer mode can be customized. User can change the low and high pass, that is the minimal altitude change that is considered as horizontal flight, and also the peak alt change to set the sound gradation in the speaker.