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