This time Futaba based.
The 6 pin “Din” connections are as follows,
Pin 1, +v (switched) Red wire.
Pin 3, “Top” pin, signal. White wire.
Shield Body, Ground. Black wire.
Plugs into the CPPM channel of a FrSky V8R7-SP.
Using a FrSky module on the pupil Tx bind the Rx to the pupil Tx.
This is the Futaba Challenger that I have fixed the FrSky V8HT (Hack) Module into.
This is an easy conversion. The hack module will fit inside where the 35mhz plug in RF board fits. I made an ally plate for the antenna, the bind button and LED fit just to the right of that. The RF module has a plug on the PCB that you can unsolder and use to connect the hack module. New plugs can probably be bought at Maplins.
The little PCB that holds the momentary switch and the LED is glued to the inside of the case with balsa wood spacers. Be careful here, I was a bit clumsy and got thin ciano on the momentary switch. I got another module and will try to locate a switch, maybe at Maplins, for the ruined unit. ( RadioSpares, part No 283-9787)
It all works very well. This is a Mode 1 Challenger. When I got it, it was Mode 2, however I believe there is no way to easily alter the wiring to convert the reverse switches etc. When I first connected it all up, the Challenger operated the wrong surfaces. When mechanically converted to Mode 1 it was fine. I had to remove the low throttle restriction plate in the gimble. I left the high throttle restriction plate in, it will stop pupils attempting to go pylon racing with the trainer when I am not paying attention.
While I thing about it, here is a link to a useful site for buddy connections.
For wireless systems, do not use the connectors that cancel the Instructors Tx RF power. This prevents the Instructors Tx from transmitting at all while the buddy plug is in the socket.