How do carb restorers clean the outside of the carb?

Hey toolmanmike, I just googled your question and the same question was posed on a chebby forum. From what was said on there, put the parts in a 50/50 mix of Simple Green and water with an ultrasonic cleaner for 1/2 hour. Here is the link......by the way dont stare directly at it, its from a chebby site
http://www.chevytalk.org/fusionbb/showtopic.php?tid/183976/

What is an ultrasonic cleaner??