Providing {HEAD ~ signal conductors} which serve only to interconnect {TAIL ~ the programmable logic elements} in each group avoids tying up much longer conductors just to make short interconnections between adjacent programmable logic elements 
serve to interconnect
Providing { HEAD ~ signal conductors } which serve only to interconnect { TAIL ~ the programmable logic elements } in each group avoids tying up much longer conductors just to make short interconnections between adjacent programmable logic elements
OTH HEAD HEAD HEAD HEAD HEAD HEAD OTH REL OTH REL 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