The pressure supply conduit communicates with {HEAD ~ an external source} of air, or {TAIL ~ a detachable cartridge} of a biologically compatible compressed gas 
The pressure supply conduit communicates with { HEAD ~ an external source } of air , or { TAIL ~ a detachable cartridge } of a biologically compatible compressed gas
OTH OTH OTH OTH OTH OTH HEAD HEAD HEAD HEAD HEAD HEAD HEAD OTH OTH OTH OTH TAIL TAIL TAIL TAIL TAIL TAIL TAIL OTH OTH OTH OTH OTH OTH