it back to the selected position reel controller 24 sensing this increase in force on lead 30 then limits the force applied to reel 14 to a level which is non destructive of the tape a steady state condition is achieved in which a slight amount of force is applied to reel 14 thereby maintaining reel 16 in a slightly displaced position a countering force is applied to reel 16 and tape 18 is maintained at a reasonable tension it is conceptually possible that this invention could be practiced with both reels rotating however the dynamics of such a system would make its operation erratic when one reel is maintained in a selected position as described herein a relatively constant tension is achieved the amount of tape on the respective reels is not a factor and the tape is maintained in the same position on the reels referring now to fig2 the tape tensioning apparatus 10 is shown in block diagram form as a servo system servo systems are well known in the industry for use in tape transport operations a representative description of such a system is described in u s pat no 4 513 229 issued apr 23 1985 for 34 reel servo for tape transport 34 motor 32 drives reel 16 shown in fig1 as represented by line 27 the shaft of the motor which rotates with reel 16 is directly connected to an optical tachometer 34 or other suitable device for sensing the position or rotation of reel 16 this sensing provides the information represented by line.