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