There is a very easy way to decode Futaba RXs using their model description. Let's consider three:
R148DF:
The R stands for receiver
The 8 stands for 8 channels
The D stands for dual conversion
The F stands for FM or PPM
R138DP:
P stands for PCM
R319DPS:
The 9 stands for nine channels
The P stands for PCM
The S stands for synthesized
As far as I know, Futaba has been using a very logical coding system for both its TXs and RXs for years!
Regards,
Suzie