If you're teaching someone to fly, there can be no safer or simpler system than by using a trainer lead between two compatible transmitters. If the student experiences a problem, control can be taken back by the instructor at the flick of a switch.
Futaba square buddy lead on both ends which will link any futaba transmitter with the new square plug on the back of the TX. Typical sets that have this plug are 6EXA, 7CAP, FF9, 10C and 14MZ
