A SHORT press of the PAGE key calls the trainer settings page:
This page allows you to configure the trainer function for "master" use (make sure the Trainer mode in model settings is set to Master). For each of the 4 main functions you will be able to set the mode (OFF, += for Add, := for Replace), ratio and input channel. Start by setting the mode for each function (the "standard" way is Replace i.e. when the trainer function is activated the function is fully transferred to the student, Add allows both master and student to act upon the function together). Then select the source channel accordingly to the brand/model of the student radio, and set the ratio to 100% for now. Now ensure the student radio is connected and recognised (moving the sticks of the student radio should change the 4 numbers at the bottom of the screen) make sure all its trims are neutral, all its sticks are centered (including throttle). Select the CAL field and press ENTER twice. The numbers should now be 0.0 or very close. Now move the student radio's sticks and check the numbers vary from -100 to +100. Should they reach those values before the stick hits the end of its travel, reduce the ratio so that the throws match. Should they never reach -100 to +100 even with full stick deflection, use the Multiplier field to increase it. Trainer input is now configured. Note that this setting is global, because it depends on the student radio regardless of the selected model. In order to use the Trainer function on a specific model you will need to assign the switch you want to the "Trainer" Custom Function for that model. More about this further.