In order to connect an angle measuring device to a brushless direct-current motor, a coupling is used, the coupling halves (10, 28) of which are each attached to the rotor (46) of the motor and/or the rotor (42) of the angle measuring device. Instead of using a coupling that is rotationally symmetrical at arbitrary angular positions as in the prior art, a coupling is used in which the coupling halves (10, 28) can be connected to one another only in a finite number of relative angular positions. An adjustment must be made before the coupling halves (10, 28) are attached to the respective rotors (46, 52). This allows all subsequent adjustment to be omitted, for example, even for maintenance work.