the first device is driven by the first power supply, and capable of performing a communication via {HEAD ~ the bus} in the condition in which the pull up voltage is equal to either of {TAIL ~ the first predetermined voltage} and the second predetermined voltage, 
the first device is driven by the first power supply , and capable of performing a communication via { HEAD ~ the bus } in the condition in which the pull up voltage is equal to either of { TAIL ~ the first predetermined voltage } and the second predetermined voltage ,
OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH HEAD HEAD HEAD HEAD HEAD HEAD OTH OTH OTH 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