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