How Teddy Ruxpin talks

A normal (non-Teddy) cassette tape is designed for stereo playback with two distinct tracks on each side for the left and right speakers. In contrast, a Teddy Ruxpin cassette uses the two tracks differently: the left track contains the audio, while the right track encodes the toy’s movements.

eddy 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 - this “buzzing” is the pulse-position modulation.

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