The second time difference may be a time difference between falling edges of {TAIL ~ the first component} of {HEAD ~ the differential signal} and the second component of the phase shifted signal 
The second time difference may be a time difference between falling edges of { TAIL ~ the first component } of { HEAD ~ the differential signal } and the second component of the phase shifted signal
OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH TAIL TAIL TAIL TAIL TAIL TAIL TAIL OTH HEAD HEAD HEAD HEAD HEAD HEAD HEAD OTH OTH OTH OTH OTH OTH OTH OTH OTH