{TAIL ~ Diode protection} 512, e.g., crossed diodes connected in {HEAD ~ parallel} with one another and with a resistor element may be connected across pairs of conductors in each circuit 
{ TAIL ~ Diode protection } 512 , e.g. , crossed diodes connected in { HEAD ~ parallel } with one another and with a resistor element may be connected across pairs of conductors in each circuit
TAIL TAIL TAIL TAIL TAIL TAIL OTH OTH OTH OTH OTH OTH OTH OTH HEAD HEAD HEAD HEAD HEAD OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH