A second circuit coupled to {TAIL ~ the oscillator} is arranged for receiving an externally provided frequency reference input at {HEAD ~ a second input node} 
A second circuit coupled to { TAIL ~ the oscillator } is arranged for receiving an externally provided frequency reference input at { HEAD ~ a second input node }
OTH OTH OTH OTH OTH TAIL TAIL TAIL TAIL TAIL TAIL OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH HEAD HEAD HEAD HEAD HEAD HEAD HEAD HEAD