The loading, {HEAD ~ unloading}, handling and processing of wafers in {TAIL ~ the machine} can occur while other wafers are being preheated 
The loading , { HEAD ~ unloading } , handling and processing of wafers in { TAIL ~ the machine } can occur while other wafers are being preheated
OTH OTH OTH HEAD HEAD HEAD HEAD HEAD OTH OTH OTH OTH OTH OTH OTH TAIL TAIL TAIL TAIL TAIL TAIL OTH OTH OTH OTH OTH OTH OTH OTH