Futaba 3pm question

I use a 3PK (FM), another of the so called computer radios - these transmit using 3 different kinds of user selected modulation schemes (oldest to most recent) - PPM - Pulse width modulation, PCM - pulse code modulation and HRS - high response system. These are diff ways of encoding/decoding the info on the FM signal. They get faster in the same order with HRS being the fastest. I would assume the 2.4Ghz system is doing the same kind of thing - they are two diff ways of modulating the signal.