{HEAD ~ The focal plane shutter} is classified into two major groups, i.e., a horizontally running screen type focal plane shutter, and {TAIL ~ a vertically running blade type focal plane shutter} 
is classified into
{ HEAD ~ The focal plane shutter } is classified into two major groups , i.e. , a horizontally running screen type focal plane shutter , and { TAIL ~ a vertically running blade type focal plane shutter }
HEAD HEAD HEAD HEAD HEAD HEAD HEAD HEAD REL REL REL OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH TAIL TAIL TAIL TAIL TAIL TAIL TAIL TAIL TAIL TAIL TAIL TAIL