This paper deals with the choice of motor and transmission with reference to the dynamic operating range of the motor and to the general case in which there is alternation of the power direction through the reducer. The paper proposes a method in which the resolving diagrams are obtained starting from the distinction between two different load torques, characterized by only direct and only inverse efficiency of the transmission respectively. In order to make the correct choice of the reducer to be coupled with a given motor, the paper also proposes a diagram that relates the transmission ratio and both the efficiencies. The guidelines for an automatized identification of all the admissible drive system-transmission couples are delin...