{HEAD ~ A motor} drives {TAIL ~ a brush} to sequentially connect the terminals to the slip ring to energize the terminals in sequence 
drives
{ HEAD ~ A motor } drives { TAIL ~ a brush } to sequentially connect the terminals to the slip ring to energize the terminals in sequence
HEAD HEAD HEAD HEAD HEAD HEAD REL TAIL TAIL TAIL TAIL TAIL TAIL OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH