During reversal the servo system which is driven into saturation senses the occurrence of zero motion of the drive mechanism and reverses {HEAD ~ the direction} of {TAIL ~ energization} of the electromagnetic drive 
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During reversal the servo system which is driven into saturation senses the occurrence of zero motion of the drive mechanism and reverses { HEAD ~ the direction } of { TAIL ~ energization } of the electromagnetic drive
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 REL TAIL TAIL TAIL TAIL TAIL OTH OTH OTH OTH