The switch assembly has {TAIL ~ three switches}, {HEAD ~ each} of which selectively illuminates one of the filaments 
The switch assembly has { TAIL ~ three switches } , { HEAD ~ each } of which selectively illuminates one of the filaments
OTH OTH OTH OTH TAIL TAIL TAIL TAIL TAIL TAIL OTH HEAD HEAD HEAD HEAD HEAD REL OTH OTH OTH OTH OTH OTH OTH