Replying to my own question, I believe the connection between "Power Input" (on camera) and a PWM output (on RC controller). Is just a simple connection between the 7.2v backup battery and and the "Power Input" on the camera. So as long as that pwn is not used, it does not matter what the pwn0? is defined as.
(I hope I'm right.)
And so the TTL-232 sends a signel to the RC controller through air?
