Abstract: An apparatus for selectively delivering incremental linear motion to a reciprocably mounted tool of a machine, for example, the shifting needle bar of a carpet tufting machine, includes means for intermittently delivering rotary power to a set of oppositely rotatable shafts each having coupling means which, during each dwell period of power delivery, are coupled to driven shafts which are linked to rotate together in the same direction; program controlled latch means are provided for selectively operating one or the other of the coupling means to provide control of the direction and duration of the transmission of motion from the power source.