HAH, at long last I can add something to one of John's posts. John always knows well about any subject and he is well endowed with good common sense approaches. He be a hard man to follow! Listen well to John.

If you have an older Airtronics receiver with standard servos, or wish to use older Airtronics servos with any other receiver, it can be done.
1. AT rcver-other servos. It's always black to black and red to red (or whatever color that constitutes same) On the servo plug in, lift the little plastic tab (here a #11 xacto blade tip works fine) holding the wires in place. Gently slide the connector leads out. Reverse and slide them back in. Be certain the plastic tab is back in the "Hold-In" position. Works!
2. Old ribbed AT servos with another receiver. File, sand, cut the ribs down to whatever will fit the new connection. Reverse the polarity as described above. Works!

FYI: JR transmitters work with Airtronics receivers, and vice versa. Same for Hitec/Futaba. Now there are so many options in receivers, especially Hitec, the choices are virtually unlimited. I will be flying on 72 mhz for a looonnnnggg time. I have one 2.4, with two receivers, and only use it for night-flying because it cuts through the neon lights. 72 gets bogged down there.