Abstract: A motor 12 has an output shaft 18. A transmission device 14 transmits rotary power, selectively, in any one of two drive modes from the shaft 18 to an output shaft 16 connected to a rotary load. The drive modes differ in respect of direction of rotation and/or speed ratio. Output pulleys 20/22 are respectively connected to intermediate pulleys 44/54 on the device 14. Auxiliary intermediate wheels 48/58, which are respectively co-axial with and connected to the pulleys 44/54, are drivingly connected respectively in accordance with the two drive modes by means of a drive element 51 to an output wheel 42 on the shaft 16. The device 14 is pivoted about the shaft 16 as shown at 36. Pivoting in one direction tightens a V-belt 50 transmitting drive to the pulley 44 and thence via the wheel 48 in a first drive mode to the shaft 16; while slackening a V-belt 60 to disconnect drive to the pulley 54. Pivoting in an opposite direction causes drive via the pulley 54 and wheel 58 to the shaft 16 in the other drive mode.