{HEAD ~ The second direction} opposes {TAIL ~ the first direction}, the first voltage has a different value than the second voltage, and the first duration is substantially the same as the second duration 
opposes
{ HEAD ~ The second direction } opposes { TAIL ~ the first direction } , the first voltage has a different value than the second voltage , and the first duration is substantially the same as the second duration
HEAD HEAD HEAD HEAD HEAD HEAD HEAD REL TAIL TAIL 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