a gear ratio detector for detecting {HEAD ~ the gear ratio} set by {TAIL ~ said variable gear ratio mechanism}, 
set by
a gear ratio detector for detecting { HEAD ~ the gear ratio } set by { TAIL ~ said variable gear ratio mechanism } ,
OTH OTH OTH OTH OTH OTH HEAD HEAD HEAD HEAD HEAD HEAD HEAD REL REL TAIL TAIL TAIL TAIL TAIL TAIL TAIL TAIL TAIL OTH