Because {HEAD ~ the Profinet system} is {TAIL ~ a real time system}, the times for LatchIN and LatchOUT of the process data are synchronized, so that data is exchanged on all Profinet devices simultaneously 
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Because { HEAD ~ the Profinet system } is { TAIL ~ a real time system } , the times for LatchIN and LatchOUT of the process data are synchronized , so that data is exchanged on all Profinet devices simultaneously
OTH HEAD HEAD HEAD HEAD HEAD HEAD HEAD REL TAIL 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