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How can I create a PPM-generating device whose output can be recorded as audio?

Dear Community,
         In the late 80s and early 90s, the whole Teddy Ruxpin craze took off, and there were many spin-offs on this.  The basic idea was that the toy had a cassette player where one channel was directed to an audio circuit in the usual way, and the other channel had animation synchronization code directed to some sort of receiving circuit which controlled motors to make the mouth and eyes move so it would appear to be telling a story or singing a song.  My favorite instance of this (which I had as a child), is the Ideal Big Bird Storymagic based on the famous Sesame Street character.  There were so-called "satellite toys", Cookie Monster and Oscar which connected to Big Bird via a special patch cord, and they talked along and helped Big Bird tell the story.  I never had those though.  Different fans tell me that the animation sync code is Pulse-position modulation, the same code used over radio waves to guide remote controlled cars and helicopters.  I'm not sure if this is true or not.  I've looked at it in a waveform editor, and there appears to be some amplitude modulation going on here too.  (Please see below).  The highlighted (white) section is the span of two words.  The right (lower) channel shows the voice speaking these two words, and the left (upper) channel shows what happens to the code (which really sounds like a fax machine) as he moves his jaw down, up, and down again in time with the words.  Is this PPM, and if not, what is it?


Now that I'm in my mid 20s, and I work with young children, I found one of these Ideal Big Birds on Ebay in great working order.   I'm wondering if it's possible to try to re-create what the manufacturers used to create this sync code in the first place.  Sesame Street created many nice "regular" story / music tapes with Big Bird as the central character.  I thought it might be cool to take some of these (especially the Follow That Bird soundtrack) and add the sync to make my own sort of unofficial storymagic tape (just for fun, and for my students, not to sel or share, as this would be a copyright issue). 
    I'm wondering if some sort of 1KHz oscillator-like device could be built that has levers of some kind, which could be routed through a DAW or a mixer, which would allow one to perform along with a program, and place the appropriate modulation envelopes into the stream of PPM to place the movements?  I think there are at least two kinds of modulation in the code; that for the beak, and for the eyes.  There must be other kinds of modulation for Cookie Monster and for Oscar.  If something like this seems practical and feasible, I'd enjoy learning about it, just for the fun of it.  If it is possible, I am also wondering how or where I could have it built, and for what sort of budget, as I am far better with my ears than with the soldering iron.  I have tried and tried, to no avail, to find someone in the “talking toys” community who knows how this was originally created.  Let me know if you'd like me to send you a clip of the audio file.  Here's a link to someone else's on Youtube so that you can see what I'm talking about.  Thank you so much for taking the time to read all of this senseless ramble!!

http://www.youtube.com/watch?v=xxCnmao8FAs

Thanks a ton for any insights that you have!!!  I apologize in advance for the inherent nutty-ness of this post! ;) 

Sincerely,
Jessica

Picture of How can I create a PPM-generating device whose output can be recorded as audio?
From WikiPedia

Teddy Ruxpin movement data is encoded as a series of rapid pulse groups known as pulse-position modulation. The data track contains continuous groups of nine pulses separated by silence. The spacing between pulses varies, and the length of each space determines the following characteristics (each of which is assigned to one of the "time slots" between two of the pulses): position of Teddy's eyes, upper jaw, lower jaw, and (if Grubby is attached) the position of Grubby's eyes, upper jaw and lower jaw. If the cassette is played in a normal cassette player, one would hear both the program recorded on it, as well as a buzzing noise - which is the PPM referenced above.


If I were you, I'd retrofit the little bugger like this

http://www.ez-robot.com/Projects/Robots/Teddy-Ruxpin-Robot-V1