Patent ID: 7729020

Claim:
A method, comprising: switching between a first and a second transmission states in response to a command for changing a moving speed of a carriage via a transmission control set; receiving transmission power from said transmission control set in the first transmission state via a first transmission set; receiving transmission power from said transmission control set in the second transmission state via a second transmission set; synchronously rotating an active gear of said transmission control set with a shaft of a step motor; engaging two follower gears of said transmission control set with said active gear for transmission by said active gear; swinging a swing arm between a first position to allow said follower gears to engage with said first transmission set and a second position to allow said follower gears to engage with said second transmission set; holding said swing arm via a holder of said transmission control set to fix the transmission control set in one of the first and second transmission states to allow said carriage to move at said selected speed; and retracting said holder to release said swing arm in order to change said moving speed of said carriage, and protracting said holder to confine said swing arm in one of the first and second positions in order to fix the transmission control set in one of the first and second transmission states for said scanning operation during rotation of the step motor in both clockwise and counter clockwise directions.