a printing unit that receives print data from {HEAD ~ the host computers} connected by {TAIL ~ said control unit}, and carries out printing processing based on the received print data, 
connected by
a printing unit that receives print data from { HEAD ~ the host computers } connected by { TAIL ~ said control unit } , and carries out printing processing based on the received print data ,
OTH OTH OTH OTH OTH OTH OTH OTH HEAD HEAD HEAD HEAD HEAD HEAD HEAD REL REL TAIL TAIL TAIL TAIL TAIL TAIL TAIL OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH