Back in the days before the internet, I had a job to design something like this (RC servo controller), I actually went to the Futaba factory and asked one of their techs how it was done, and he gave me the whole spec. It's PWM at a constant PRF; I don't remember the exact numbers but that Wiki article is pretty accurate as far as it goes.
Cheers! Rich
Rich Grise wrote in news:pan.2008.07.17.16.54.18.902204 @example.net:
I think they just XOR the control pulse with a one-shot timed by a pot on the servo shaft to generate a motor control signal. The pot value dictates the nature of the width of the control pulse, and there's a ton of wiggle room in the frequency.
C-band Sat TV equipment used a servo to select vertical or horizontal polarization. The basic receivers used a 555 timer IC to generate the signal, and pair of pots to set the two positions.
"Rich Grise"
** The fact is that, like all other hobby RC radio system makers, Futaba call the method ** PPM**.Often " PPM" is marked right on the transmitters.
It is never called PWM.
It is also standard practice to label transmitters as being " FM " - when the modulation method is actually ( narrow band) FSK.
..... Phil
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