1. The input shaft gives the motion of the gear train; known as the drive. Then the output shaft receives the motion, being the driven gear.
2. The drive gear is the gear on the right, the idle gear is the one in the middle and the driven is the gear to the left.
3. The speed of the gear train is at a constant speed.
4. The torque of the gear train is at a constant level.
5. The gear ratio is 1:2:1.
6. Yes, you can make the input shaft turn by turning the output shaft, getting to a conclusion that the flow of the power is reversible.
7. The input and output gear moves in the same direction because the idler makes them turn into the same way.
8. The direction of travel would be different for the input and output gears without the idler.
9. This mechanism is used in motorcycles, clocks, cars and other amazing objects.
“Don't cry because it's over, smile because it happened.” ~ Dr.Seuss