| 摘要 |
<p>Disclosed herein is a control comprising a rotatably supported wheel, a first direct current motor, means drivingly connecting the first direct current motor to the wheel with a first drive ratio, a second direct current motor, means drivingly connecting the second direct current motor to the wheel with a second drive ratio lower than the first drive ratio a source of direct current, and a switch electrically connected to the source of direct current and to the first and second direct current motors and including a contact arm for initially electrically connecting the direct current source to the first direct current motor whereby to drive the wheel at a slow speed, and for subsequently additionally electrically connecting the source of direct current to the second direct current motor while maintaining electrical connection of the direct current source to the first direct current motor, whereby to drive the wheel at a fast speed.</p> |
