By means of such an arrangement intermediate positions of {HEAD ~ the guide disc} can also be effected, while {TAIL ~ a very compact configuration} of the positioning unit is obtained at the same time 
By means of such an arrangement intermediate positions of { HEAD ~ the guide disc } can also be effected , while { TAIL ~ a very compact configuration } of the positioning unit is obtained at the same time
OTH OTH OTH OTH OTH OTH OTH OTH OTH HEAD HEAD HEAD HEAD HEAD HEAD HEAD OTH OTH OTH OTH OTH OTH TAIL TAIL TAIL TAIL TAIL TAIL TAIL TAIL OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH