An access control system for restricting access through a passageway includes a shaft rotatable about a central axis; a barrier fixed to the shaft to rotate therewith; and a brake assembly. The brake assembly includes a sun gear rotatable about the central axis, a carrier, and a ring gear, wherein one of the carrier or the ring gear is fixed against rotation and the other of the carrier or ring gear is connected to the shaft to rotate therewith. A plurality of planet gears are rotatably connected to the carrier, each planet gear being disposed between and engaging with each of the sun gear and the ring gear. An electromagnetic brake comprises an electromagnet and an armature. The armature is connected to or integral with the sun gear to rotate and move axially therewith. At least one of the electromagnet or the armature is moveable between an operative position and an inoperative position.