 Instead of idler gears, of course, a toothed belt or a roller chain can be used to transmit torque over distance.For short distances, a train of idlers may be used; whether an odd or even number is used determines whether the final output gear rotates the same direction as the input gear or not.For longer distances, a roller chain or belt is quieter and creates less friction, although gears are typically stronger, depending on the strength of the roller chain.