{HEAD ~ a first diode} disposed in {TAIL ~ series} between the first power supply and the signal line so as to allow supply of the pull up voltage from the first power supply to the signal line and to block flow of a current from the second power supply to the first power supply, 
disposed in
{ HEAD ~ a first diode } disposed in { TAIL ~ series } between the first power supply and the signal line so as to allow supply of the pull up voltage from the first power supply to the signal line and to block flow of a current from the second power supply to the first power supply ,
HEAD HEAD HEAD HEAD HEAD HEAD HEAD REL REL TAIL TAIL TAIL TAIL TAIL OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH