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