Each module has a housing divided by walls into {HEAD ~ a transfer chamber} at {TAIL ~ one end} and a second chamber at the other end 
at
Each module has a housing divided by walls into { HEAD ~ a transfer chamber } at { TAIL ~ one end } and a second chamber at the other end
OTH OTH OTH OTH OTH OTH OTH OTH OTH HEAD HEAD HEAD HEAD HEAD HEAD HEAD REL TAIL TAIL TAIL TAIL TAIL TAIL OTH OTH OTH OTH OTH OTH OTH OTH