{HEAD ~ Each} of {TAIL ~ the individual discs} can be actuated, with the interposition of a stepping mechanism, via a push button which is adjacent to the viewing windows 
{ HEAD ~ Each } of { TAIL ~ the individual discs } can be actuated , with the interposition of a stepping mechanism , via a push button which is adjacent to the viewing windows
HEAD HEAD HEAD HEAD HEAD REL TAIL TAIL TAIL TAIL TAIL TAIL TAIL OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH