There are a couple of not quite correct statements in the above. PCM is no more immune to interferance than PPM is, it just sits and waits for a good signal to come along. If one does in a few milliseconds, then it continues to work as asked, if not it goes into failsafe which can be set up by the user to be a specific control position. If the interferance is intermittent, you will get what appears to be very slow reaction from the plane, maybe enough to save it from crashing. If using PPM, you can now also get the same failsafe features in some equipment (check out FMA for instance) but it is not common. One big advantage of PPM is that, if interferance is present, you usually know it before you take off and any sensible reaction is to abort the flight. PCM requires more bandwidth than PPM so limits the period between subsequent channels, i.e. aileron, elevator, throttle, etc., to a longer period than PPM uses. While this is not normally a critical issue, if you try to cram to many channels into a frame, frame rate will be much less for PCM.