Gas Eggconomizer is {HEAD ~ a visual display device} which indicates {TAIL ~ the rate} of fuel consumption in an internal combustion engine 
indicates
Gas Eggconomizer is { HEAD ~ a visual display device } which indicates { TAIL ~ the rate } of fuel consumption in an internal combustion engine
OTH OTH OTH HEAD HEAD HEAD HEAD HEAD HEAD HEAD HEAD OTH REL TAIL TAIL TAIL TAIL TAIL TAIL OTH OTH OTH OTH OTH OTH OTH OTH