Abstract: An angular non return device is provided associated with a turnstile (1) having an axis X and capable of acting at will in one or the other direction. This device comprises a drum of revolution (2) integral with the turnstile and coaxial therewith, a fixed vee (3) whose bisecting plane contains the axis X, a roller (4) interposed between the vee and the drum and mounted on a lever (5) so that it may be moved between a first end position in which it is locked by jamming between the drum and a face (3.sub.1) of the vee and a second end position in which it is locked by jamming between the drum and the other face (3.sub.2) of the vee, and electromagnetic elements (6 to 10) for urging the roller at will towards one or other of its two end positions. Portions (14, 15) of the drum are recessed so as to prevent locking of the turnstile in certain angular positions.