Campy is right. Also, it is my understanding that PCM has been an ever-evolving thing. Therefore, the PCM protocol used in the mid-90's by futaba might be different from the one used today. Therefore, you might not even be able to find a rx for that tx. Sell it, or give it away, and get you a good, new tx that will do both (most now a-days will do both, PPM and PCM).