With {HEAD ~ the presence} of {TAIL ~ a corresponding control signal} a line switching connection is established from the first switch to the second switch and the data are then transferred through this connection 
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With { HEAD ~ the presence } of { TAIL ~ a corresponding control signal } a line switching connection is established from the first switch to the second switch and the data are then transferred through this connection
OTH 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