My "new" Mecablitz 60 CT-4 has several numbers on the back that are hard to read. I assume they are supposed to be back lit by an LED. The more I research it the more I realize that there were multiple versions of the Mecablitz 60 CT-4. Some manuals show controls that aren't on mine. Apparently there are some that emit an audible tone. Mine is dead silent... except a POP when it lights up like the Fourth of July So are these numbers suppose to be constantly back lit or do they only light up in a certain mode?