How does a turnstile work?

A person can open the passage way with kind of access control systems, card reader systems, remote control systems, biometric systems, ticket accepting devices etc.
It is a post with a number of short poles sticking out from it that have to be pushed round as each person walks through the entrance.
After a person has passed, the turnstile arms locking again immediately.
They can allow only one-way passage or bidirectional use.
In case of fire or any similar emergency situation, free exit option is available.
If a turnstile is lock while power off, it has been called fail secure turnstile. If a turnstile is free while power off, it has been called fail safe turnstile.

Turnstiles often use ratchet mechanisms to allow the rotation of the stile in one direction allowing ingress but preventing rotation in the other direction.
A lock up arm (pawl) is used to locking at the turnstile mechanism.
Solenoid pushes or pull the pawls.
A drive spring provides the turnstile arm to return its correct position when passage occurs. Drive spring mechanism has a spring inside its housing used to store mechanical energy. If this spring is compressed more than desired, force applied to turnstile arm rotating force will increase.
Shock absorber provides the smooth operation of the turnstile. Kinetic energy of the arm is absorbed by the shock absorber while arm comes to its original place.
Proximity switches are used to received passage information or position of arms.

Controlled Access System