Actually Multiplex did it first and said they were either fazing out PCM or not going to use it at all, I fergit. Then Mr. marks came out with the SMART technology.
Multiplex does not produce any PCM anymore and they are the ones that introduced PCM in the first place.. They are now using the IPD receivers .
FMA as was suggested by another poster, seems to have one of the best receivers but at only 5 channel, I'll wait for some more channels.