Rotation is transmitted from driving shaft a through gears 1, 2, 3 and 4 to driven shaft b. Gears 1 and 4 are keyed on shafts a and b. Gears 2 and 3 rotate freely on studs carried by drum housing d. Clutch member c is keyed to shaft b. When clutch c is engaged and brake drum d is released, shafts a and b rotate at the same speed and in the same direction. When clutch c is engaged and drum d is braked, shafts a and b rotate in opposite directions with the transmission ratio i_ab=-z₄/z₁ where z₁ and z₄ are the numbers of teeth of gears 1 and 4. When clutch c is disengaged and drum d is released, planetary gears 2 and 3 roll around sun gears 1 and 4, and shaft b is stationary if a resisting torque is applied to it.
$2856$CxG,SR$