Here is a brief history about all of the various sound systems that have been used in Disneyland.
From soundandcommunications.com:

Here’s a bit of fun looking back. I was able to talk with and work with guys who had originally set up the Disneyland Electrical Parade perhaps the most viewed parade in history. When it originally debuted in 1972, the parade had the first show-control system in existence. A Berkey Colortran “computerized” lighting console, if I recall correctly, was used to trigger audio, lighting and machinery to operate the parade. One of our sound-shop technicians figured out that the console’s control output of 0-10V could be configured to control some ITC radio-station VCAs, two of which were available per each parade zone. In front of the VCAs was a custom Disneyland router controlled by the console’s “non-dim” outputs.

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