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