means responsive to the reciprocable means for generating {TAIL ~ pulses} in response to {HEAD ~ increments} of movement of the reciprocable means 
means responsive to the reciprocable means for generating { TAIL ~ pulses } in response to { HEAD ~ increments } of movement of the reciprocable means
OTH OTH OTH OTH OTH OTH OTH OTH TAIL TAIL TAIL TAIL TAIL OTH OTH OTH HEAD HEAD HEAD HEAD HEAD OTH OTH OTH OTH OTH OTH