I didn't suggest there was any incompatibility. I didn't see anything about 50hz there and I don't see that it matters either way. The frequency at which the pulse is repeated is probably not critical anyway. I'm no expert in servo design but my understanding is that the pulsewidth is the critical spec because that's what changes when the servo receives commands. When you watch the servo pulsewidth on a scope , you're seeing the same 1500uS pulse with either servo. The difference is that your seeing it 4 times more often with the faster digital servos, but if you receive only one bill every month do you have to pay any more if you receive 4 copies of the same bill (one a week) during that month ? (crude analogy , I admit) but my point is that the servo must obeay a command to set it's pulse width some value whether it receives the same command 50 times a second or 200 doesn't change the command. If I have this all wrong please tell me because I do want to know. I'm just saying that is my understanding of it as it stands at the moment.