About Furby's Insides

Schematic
Chris Brown(chris_furby@yahoo.com) sent in this schematic of the Furby circuit boards.  Let him know if you have any comments or  errors to report about it.  The schematic is in pdf format.  You'll need Adobe's Acrobat Reader.  THANKS CHRIS!

Autopsy
First, take a look at the Furby Autopsy site over at phobe.  They've done a great job opening the guy up and documenting what they saw.  In particular, the data at their FAQ, HACKFAQ, and GUTS pages is very interesting.  The HOWTO page tells you, well, how to do it yourself!

Extra's
Took the fur and shell off of my Furby(as described in the furby autopsy).  Keep in mind there are 6 screws(two are under the foam padding).  It is easy to trace each of the stimuli to their connections on the circuit boards.  Following the connections from there is another story!
As phobe notes, there are two daughtercards that are covered in plastic goo(to prevent reverse engineering).  There are also 4 ICs visible.  Here is what we know about them:

1 is a serial eeprom. HT93LC46 9834W8021-1.  It has 8 pins and is located between the large daughtercard and the back button.  It is built by MicroChip technology and has a data sheet here.  I think it is data storage only.

2 is a Hex Inverting Schmitt Trigger.  Whatever that means.  It has 14 pins and is located near the connection to the battery, the IR, the MIC and the food sensor connection. National Semiconductor made it.  P78TN MM74HC 14M.  Data sheet.

Lee Hunt wrote in with information about this chip.
(Hex Inverting Schmitt Trigger)
Looking at the datasheet, it's a hysteresis switch.  That is, a switch that turns on when the input voltage reaches a certain threshold, but will stay on until the input voltage is significantly lower.
I suspect it's being use to "debounce" furby's sensors; or at least to let furby to "keep his attention" once a certain stimulus (e.g. light) has been recorded.

3 is very hard to see.  It is under EVERYTHING.  It has many pins.  To see the designation, you'd need to take apart the furby almost completely.