Whether a particular transmitter can be used as a buddy box with a Futaba 2.4 transmitter is not just a matter of finding a cord that fits both transmitters. While you do need the right cord, you also need one of the transmitters listed in the manual for your radio. The Futaba 7C-2.4 manual says you can use any Futaba transmitter that fits the cord (this is an improvement over the 6-channel Futaba, which was incompatible even with some other Futaba transmitters). Whether another brand would work is something you'd have to find out by trial and error or from someone else who has tried what you propose to use. Many Futaba transmitters will work with Hitec transmitters as buddy boxes; this one I don't know about.