Path: utzoo!utgpu!jarvis.csri.toronto.edu!cs.utexas.edu!samsung!aplcen!haven!udel!berryh
From: berryh@udel.edu (John Berryhill)
Newsgroups: sci.electronics
Subject: Teddy Ruxpin's Audio Frequency Modulatinon
Message-ID: <12595@nigel.udel.EDU>
Date: 1 Mar 90 05:33:16 GMT
Sender: usenet@udel.EDU
Reply-To: berryh@udel.edu (John Berryhill)
Organization: University of Delaware
Lines: 23


Teddy uses a stereo head with music on one channel and data on the
other.  Not having a storage scope handy, it's tough to get a good
look at the data channel except for those moments when the tape
holds one facial expression long enough to get a picture of it with
the scope camera.  The data packets are about 8 milliseconds
long with 4 milliseconds between them.  Inside each packet is some
sort of triangle wave that has a variable delay at the upward zero
crossing, i.e.
	 /\        /\         /\
	/  \      /  \       /  \       and so forth (about 8 per packet)
 0----      \  /--    \  /---    \  /
	     \/        \/         \/
Has anybody out there managed to figure out what sort of modulation
this sucker uses?  I've been able to get him to partially close his
eyes and hold his mouth wide open using two function generators (a
square-modulated plain triangle wave recorded on audio tape), but
twiddling the frequencies and duty cycle doesn't seem to do anything
for him.

--
							      John Berryhill
					   143 King William, Newark DE 19711