In the video the Turnigy 9XR radio with open9x is used as a trainer. The exact same setup also applies to Flysky 9x or Turnigy 9x radios with open9X.
I used a Turnigy 9x as student radio, but could just as well have used pretty much any
Setting up a radio with open9x to act as a trainer is a bit more complicated compared to most radios. The reason is that nothing is taken for granted. With other radios the channel order of the student and the limits of the signal from the student are often hard coded. This makes it easy to connect two radios from the same manufacturer, but often very complicated or even impossible to connect two radios of different origin.
Open9x is in the other hand freely configurable. As long as a radio can produce a standard PPM stream (the information sent in the trainer cable) it will be possible to connect it successfully to a 9x or 9xr radio.
The negative side of the possibility to use most radios as students, is that you have to set up all aspects of the student/trainer link even if you are connecting to another open9x radio. It is actually not any advantage to use a 9x radio as student.
The trainer functionality is by default not enabled. This means that it is necessary to do the following four steps to control a specific model from a student radio:
1) First set up the trainer radio to accept input from the student
2) Then set up each student channel to control the correct flight surface in the trainer. The throttle channel from the student should affect the throttle in the trainer etc.
3) Calibrate the input signal.
This setup only needs to be done once and repeated only if another student radio is connected.
4) Please note that no trainer switch is defined or enabled by default. The final configuration step is to define the switch that is used to control if the trainer radio or the student radio is in control. This has to be defined in the setup for each model. I do not see the value of using different trainer switches between models. Neither do I understand why anyone would like to use anything else than the trainer switch, but if anyone wants to, the possibility is there.
The easiest way to explain the setup is in a video so here goes: