{HEAD ~ A scanning head} 7, wherein {TAIL ~ each} of the three electric motors is connected with its own negative resistor, each resistor having a resistance value that is adjustable independent of the other two negative resistors, by means of hardware or software 
wherein
{ HEAD ~ A scanning head } 7 , wherein { TAIL ~ each } of the three electric motors is connected with its own negative resistor , each resistor having a resistance value that is adjustable independent of the other two negative resistors , by means of hardware or software
HEAD HEAD HEAD HEAD HEAD HEAD HEAD OTH OTH REL TAIL TAIL TAIL TAIL TAIL OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH