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OpenTX - Application Note 05

Control Audio Volume With A Slider

Set up a rotary slider to control the volume of announcements and music..


A special function is used to make a slider control the volume and a switch position pre-flight check is used to check the volume is not too low when the model is selected.

Set Slider to Control Volume

The default setting of the master volume is made by the ‘Sound – Volume’ parameter found on the Radio Setup screen. Its default value is 50%. This can be overridden by using a special function.

First select your model and then display the ‘Special Functions’ screen. A special function which sets up the left rotary slider LS to control the master audio volume is as follows.


Function Number



Parameter 1

Parameter 2

Check Box





□ ticked


This volume control must be set up for each model, otherwise the Radio Setup value applies.

Preflight Check of Volume Level

If the slider that controls the volume is turned down too far on power up or when the model is first selected, important audio warnings may not be heard. To ensure the volume is an audible level, in the Model Setup screen under Pre-Flight Checks, set the Pot Positions to Manual. Ensure the LS pot is selected (black square background means selected), set the LS pot to the audible level you normally use it at, press ENT LP to record the pot setting and press Exit. If the pot is not at this setting during the pre-flight check, the switch warning screen is displayed. Move the pot to the required value to satisfy the check. Mid volume is a reasonable level to startup with.


Note that if you turn down the volume to quieten telemetry announcements, for example, the volume of warnings will also be turned down. It is recommended to have a separate switch to turn on and off telemetry announcements so that warnings can still be heard.

Adjust the volume to compensate for noisy environments.


Phantom Divide


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