A control cam is formed on {HEAD ~ a first transmission linkage} and a feeler roller is rotatably mounted on {TAIL ~ a second transmission linkage} 
A control cam is formed on { HEAD ~ a first transmission linkage } and a feeler roller is rotatably mounted on { TAIL ~ a second transmission linkage }
OTH OTH OTH OTH OTH OTH HEAD HEAD HEAD HEAD HEAD HEAD HEAD HEAD OTH OTH OTH OTH OTH OTH OTH OTH TAIL TAIL TAIL TAIL TAIL TAIL TAIL TAIL