The 3 arms turnstile is rotates in a circle with a single or bi-directional passage way. The mechanical version would requires the person push one arm to initiate the rotation. The semi-automatic and automatic have the turnstile locked and need to engage by an access control system or guard pushing the release button.
Tripod Turnstile Gate is control huge pedestrian traffic solution with three revolving arms. It is the most popular type and first option for stadium, subway station, factory and bus stop.