Originally Posted by Tim K
My search fu is weak today. Will a DX7 and DX4 talk to each other with a trainer cord?
Yes they will as long as you get a proper Spektrum trainer cable (or other good brand such as Expert from Horizon).
Audio cables sometimes work but are the most common source of problems with trainer setups. Also they are often too short and too stiff.
Remember that the student transmitter must have batteries and must be turned OFF. The master transmitter controls the model and must be turned ON.