Toothed pinion 1 and internal gear 2 rotate in the same direction about fixed axes A and B. Taking the sign of the angular velocities ω₁ and ω₂ of pinion 1 and gear 2 into account, the transmission ratio of the mechanism is i₁₂=ω₁/ω₂=r₂/r₁=z₂/z₁ where r₁ and r₂ are the pitch radii and z₁ and z₂ are the numbers of teeth of pinion 1 and gear 2.
$2302$SG,3L$