Abstract: An electromagnetic gear-clutch assembly (1) is disclosed. The device comprises a gear (10) having grooves (10c) that open inwardly toward the axis and extend axially. A hub (12) is located within the gear (10) where it is capable of rotating within the gear (10). The hub (12) has grooves (12k) that open outwardly away from the axis and extend axially. Keys (17) are located within the grooves (12k) of the hub (12) and are capable of moving radially toward and away from the axis, the arrangement being such that when the keys (17) are permitted to move away from the axis, at least one will enter one of the grooves (10c) in the gear (10) to couple the gear (10) and huh (12) so that they will rotate in unison. The device also comprises an actuator assembly (3) for effecting radial displacement of the keys (17).