I did some work on RC transmitters and receivers some time back.
The format was AM, which was modulated by pulses which
turned the carrier off.  Each frame consisted of 8 pulses, which gave
7 channels of proportional control.  The space between each pulse
in the train was 1.00 ms for neutral, .50 ms for one stop, and 1.50 ms
for the other stop.  The frame rate is not critical, and was about 30
per second.  The pulse train is clocks a 1 through a parallel out shift
 register,
which separates the frame into the channels.  After the first pulse, the
data returns to 0.  The pause between each frame resets the data to 1.
Each SR output is a single pulse whose width is fed to its servo circuit,
which positions both the flight surfaces, and a potentiometer so as
to null out the difference in length between the data pulse and a locally
generated pulse.  I would suppose that this system is still in use.



-----Original Message-----
From:   Sean Breheny [SMTP:sbreheny@CSRLINK.NET]
Sent:   Thursday, July 31, 1997 1:08 AM
To:     PICLIST@MITVMA.MIT.EDU
Subject:        RC Servo PWM format

Hello all,

I am trying to find out the specs on the servo control signal for radio
control servos (i.e. futaba servos for RC aircraft). I need to know how long
a pulse is for
neutral position, how long for each extreme of throw, what the pulse
frequency is, and what the voltage is. I am considering making several
PIC-based RC related projects, including a signal loss detector, autopilot,
and maneuver record/playback
device.

Thanks,
Sean