{HEAD ~ A gas blast switch} has {TAIL ~ a housing} which encloses an arcing chamber, an accumulator space and an expansion space 
has
{ HEAD ~ A gas blast switch } has { TAIL ~ a housing } which encloses an arcing chamber , an accumulator space and an expansion space
HEAD HEAD HEAD HEAD HEAD HEAD HEAD HEAD REL TAIL TAIL TAIL TAIL TAIL TAIL OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH