After the head portion 46 is sensed by {TAIL ~ the magnetic sensor} means 58, a signal is sent to {HEAD ~ an active controller} 50 
After the head portion 46 is sensed by { TAIL ~ the magnetic sensor } means 58 , a signal is sent to { HEAD ~ an active controller } 50
OTH OTH OTH OTH OTH OTH OTH OTH TAIL TAIL TAIL TAIL TAIL TAIL TAIL OTH OTH OTH OTH OTH OTH OTH OTH HEAD HEAD HEAD HEAD HEAD HEAD HEAD OTH