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 {HEAD ~ the other two negative resistors}, by means of hardware or software 
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 { HEAD ~ the other two negative resistors } , by means of hardware or software
OTH OTH OTH OTH OTH OTH 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 HEAD HEAD HEAD HEAD HEAD HEAD HEAD HEAD HEAD OTH OTH OTH OTH OTH OTH OTH