English to French Tech/Engineering Mechanics / Mech Engineering Industrial Machinery such as Trommels, Screeners, Crushers, etc

The document is a Sales Presentation.
We're talking about a Compost Screener here. A "live head" is apparently an option of the machine. I have found that in this context "live" may be "sous tension" or "mobile" but there is no mention of electrical power at this point in the text.
A "head" here may be a "poupée", une "tête", un "pied", and even une "hauteur de charge"!
Can anybody help?

For reference only : http://www.globalrepair.ca/trommel screener.htm