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