Furbys, Furby Babies, Shelbys and other Furby Friends released during 1998-2002 use a common infrared protocol for communication.
Information[]
Original 1998 Furbys have 16 different messages while the later toy series (Furby Babies, Shelby) add 16 extra[1] allowing for more unique phrases and games during interaction while retaining backward compatibility, thus all models using infrared communication can interact with each other.
Infrared is also used inside Furby's gearbox, where a beam shines through a gear to track the number of rotations.
All Furdish speaking Furby fakes, as well as some others such as Marmo, are also known to be compatible.
A Game Boy Color game, Dancing Furby, could also use the infrared port of the console for making a Furby perform various actions.
Some official accessories, namely the Furby Chatterlinks and the Sleepy Time Bed also employ infrared signals.
A close-up of a Furby's two infared sensors and single light sensor (Left and right, middle respectively)
While infrared rays on the wavelength used are completely or almost completely invisible to the human eye, many cameras will capture the communication as bright flashes of light coming from the Furby's forehead.
Example of a camera picking up a Furby's infared sensor flashing.
Technical details[]
Oscilloscope view of an infrared packet (message #5, "Party!")
The communication works by sending pulses of infrared light. A "one" bit consists of two 200 microsecond pulses with 800 microsecond delays in between (on 200, off 800, on 200, off 800). A "zero" is a single 200 microsecond pulse followed by a 1800 microsecond delay (on 200, off 1800). There's a lot of tolerance for the pulse width values, the examples above are for reference.
The pulses can be transmitted directly or with a 38 kHz carrier frequency as many remote controls do.
The message number (0 to 15) is encoded as four bits, LSB-first - for example, the number 7 would be encoded as 1110. The entire data packet consists of a "1" start bit, the message number and the bitwise inversion of the message number (e.g. 1110 -> 0001) as a checksum. When transmitted by a Furby, the message is repeated several times for reliability, with 82 millisecond delays between the packets. That number makes a single packet last exactly 100 milliseconds.
The packet seen on the oscilloscope image is "1 1010 0101", corresponding to the number 5.