Abstract: Two-way pedestrian access control system comprising a passageway laterally bounded by two pillars, said passageway being normally barred by a barrier locked in close position which can be opened upon validation by a system for recognizing individuals or passes, said barrier comprising a turnstile mounted to one of the pillars and consisting of three arms assembled in conformance with the edges of a regular trihedron and having an axis of rotation confounded with the ternary axis of symmetry of the said turnstile, said axis of rotation being so directed that the turnstile's rotation by 2/3.pi. about said axis always places an arm in horizontal position, barring the passageway, wherein said barrier further comprises a swinging gate, hinged about a vertical axis lying in the vertical plane containing the said rotational axis of the turnstile, said gate having a cutout enabling passage therethrough of the arms of the turnstile and being high enough to prevent from passing an individual of average size.