The first use of Audio-Animatronics was for Walt Disney's Enchanted Tiki Room in Disneyland, which opened in June, 1963. The Tiki birds were operated using digital controls; that is, something that is either on or off. Tones were recorded onto tape, which on playback would cause a metal reed to vibrate. The vibrating reed would close a circuit and thus operate a relay.
The relay sent a pulse of energy (electricity) to the figure's mechanism which would cause a pneumatic valve to operate, which resulted in the action, like the opening of a bird's beak. Each action (e.g., opening of the mouth) had a neutral position, otherwise known as the "natural resting position" (e.g., in the case of the Tiki bird it would be for the mouth to be closed). When there was no pulse of energy forthcoming, the action would be in, or return to, the natural resting position.
This digital/tone-reed system used pneumatic valves exclusively--that is, everything was operated by air pressure. Audio-Animatronics' movements that were operated with this system had two limitations. First, the movement had to be simple--on or off. (e.g., The open and shut beak of a Tiki bird or the blink of an eye, as compared to the many different positions of raising and lowering an arm.)
Second, the movements couldn't require much force or power. (e.g., The energy needed to open a Tiki Bird's beak could easily be obtained by using air pressure, but in the case of lifting an arm, the pneumatic system didn't provide enough power to accomplish the lift.) Walt and WED knew that this this pneumatic system could not sufficiently handle the more complicated shows of the World's Fair.
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