The light bulb has three filaments which separately emit {HEAD ~ white light} upon {TAIL ~ selective illumination} 
upon
The light bulb has three filaments which separately emit { HEAD ~ white light } upon { TAIL ~ selective illumination }
OTH OTH OTH OTH OTH OTH OTH OTH OTH HEAD HEAD HEAD HEAD HEAD HEAD REL TAIL TAIL TAIL TAIL TAIL TAIL