the motor turns the gears in the gear head assembly and the drive gears 200 the drive gears 200 mesh with the rack gears 120 on the pivot disc 50 when the drive gears 200 turn the carrier member 150 moves referring to fig3 three different carrier member 150 movements are possible a carrier member 150 not shown in fig3 located on pivot disc 50a may advance forward to pivot disc 50b turn to the left or right and advance to pivot disc 50d or 50e and turn u00b1 180 u00b0 and advance to the pivot disc 50c behind the original location to advance forward to the next pivot disc 50b the computer 215 must turn on the electrical power at the first pivot disc 50a the carrier member 150 moves forward onto the next pivot disc 50b until the electrical contacts 210 of the carrier member 150 no longer make contact with the contacts 110 on the first pivot disc 50a the computer 215 through monitoring the current levels on the first pivot disc 50a turns the power off at the first pivot disc 50a and turns on the power at the second pivot disc 50b once the carrier member 150 is completely on the second pivot disc 150b the computer 215 turns off the power at the second pivot disc 50b to move the carrier member 150 to the pivot discs 50d or 50e to the right or left of the original pivot disc 50a it is first necessary to rotate both pivot discs 50a and 50d or 50a and 50e 90 u00b0 so that the longitudinal axes of horizontal shafts 90 mounted on.