{HEAD ~ a single, hermetically sealed housing} including a metal base plate and {TAIL ~ a housing cover}, or cap sealed thereto 
{ HEAD ~ a single , hermetically sealed housing } including a metal base plate and { TAIL ~ a housing cover } , or cap sealed thereto
HEAD HEAD HEAD HEAD HEAD HEAD HEAD HEAD HEAD HEAD REL OTH OTH OTH OTH OTH TAIL TAIL TAIL TAIL TAIL TAIL TAIL OTH OTH OTH OTH OTH