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