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