Abstract: A multiple speed ratio power transmission apparatus, comprises input mechanism adapted to be connected to a power source for being driven with a constant reciprocating or oscillating motion, output mechanism including a rotatable output shaft, motion transmitting mechanism for controllably coupling the input mechanism to the output means, the motion transmitting means including an energy connecting element drivably connected to the input mechanism so as to be driven into a reciprocating or oscillating motion with a selectively, discretely variable stroke S=NS.sub.min, where S.sub.min is an increment of movement of the energy connecting element corresponding to one complete motion of the input mechanism and N=1,2,3, etc. indicating a selectively variable number of complete motions of the input mechanism, the energy connecting element being drivably connected to the output shaft for driving the output shaft through 180.degree.