Each transformer 28, in association with the link 18, thus serves to transmit signals between the surface installation 16 and {HEAD ~ the tool} in {TAIL ~ question} 
Each transformer 28 , in association with the link 18 , thus serves to transmit signals between the surface installation 16 and { HEAD ~ the tool } in { TAIL ~ question }
OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH HEAD HEAD HEAD HEAD HEAD HEAD REL TAIL TAIL TAIL TAIL TAIL