Communication between JavaScript and Macromedia Flash

"For communication between the browser (JavaScript) and the plugin (ActionScript) we need an extra technology that opens a connection between the two. Neither the browser itself nor the Flash plugin takes care of this all by itself."

Links for the proof o' concept:

Macromedia - Flash TechNote An example of communication between _JavaScript and Macromedia Flash
http://www.macromedia.com/cfusion/knowledgebase/index.cfm?id=tn_15683#ftjc

IE 6.0 - _Javascript - ActionScript and _JavaScript
http://www.quirksmode.org/js/flash_call.html