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