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