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