{HEAD ~ the first circuit}, filter and oscillator constitute a phase locked loop to synchronize {TAIL ~ the internal clock signal} to the externally provided clock signal 
{ HEAD ~ the first circuit } , filter and oscillator constitute a phase locked loop to synchronize { TAIL ~ the internal clock signal } to the externally provided clock signal
HEAD HEAD HEAD HEAD HEAD HEAD HEAD OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH TAIL TAIL TAIL TAIL TAIL TAIL TAIL TAIL OTH OTH OTH OTH OTH OTH