The frequency reference input is selectively at one of a first or second fixed voltage level designating a first or second oscillator frequency, and a variable signal level designating {HEAD ~ a frequency} between {TAIL ~ the first and second oscillator frequencies} 
The frequency reference input is selectively at one of a first or second fixed voltage level designating a first or second oscillator frequency , and a variable signal level designating { HEAD ~ a frequency } between { TAIL ~ the first and second oscillator frequencies }
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 REL TAIL TAIL TAIL TAIL TAIL TAIL TAIL TAIL TAIL TAIL