a user interface for receiving user input to enable tracking wherein the user input is received via a user interface that enables {TAIL ~ the user} to manually enable {HEAD ~ tracking}, to disable tracking or enable automatic triggering of tracking 
a user interface for receiving user input to enable tracking wherein the user input is received via a user interface that enables { TAIL ~ the user } to manually enable { HEAD ~ tracking } , to disable tracking or enable automatic triggering of tracking
OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH TAIL TAIL TAIL TAIL TAIL TAIL OTH OTH OTH HEAD HEAD HEAD HEAD HEAD OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH