The discharge vessel encloses {HEAD ~ a discharge space} having {TAIL ~ an ionizable filling} which, in addition to Hg, contains a quantity of iodide of Na, Tl, Ho and Ca 
The discharge vessel encloses { HEAD ~ a discharge space } having { TAIL ~ an ionizable filling } which , in addition to Hg , contains a quantity of iodide of Na , Tl , Ho and Ca
OTH OTH OTH OTH HEAD HEAD HEAD HEAD HEAD HEAD HEAD REL TAIL TAIL TAIL TAIL TAIL TAIL TAIL OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH