{HEAD ~ Other sensors} can use {TAIL ~ LEDs} tuned to frequencies which are absorbed in different amounts by the gases typically used for welding 
use
{ HEAD ~ Other sensors } can use { TAIL ~ LEDs } tuned to frequencies which are absorbed in different amounts by the gases typically used for welding
HEAD HEAD HEAD HEAD HEAD HEAD OTH REL TAIL TAIL TAIL TAIL TAIL OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH