the means for providing a reference signal including means for providing a clocking signal of selected frequency and means responsive to the generated pulses and to the clocking signal for generating a signal representing {HEAD ~ the difference} in frequency between {TAIL ~ the generated pulses} and the clocking signal 
the means for providing a reference signal including means for providing a clocking signal of selected frequency and means responsive to the generated pulses and to the clocking signal for generating a signal representing { HEAD ~ the difference } in frequency between { TAIL ~ the generated pulses } and the clocking signal
OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH HEAD HEAD HEAD HEAD HEAD HEAD OTH OTH OTH TAIL TAIL TAIL TAIL TAIL TAIL TAIL OTH OTH OTH OTH