The main element of an access control system is a locking device (electric locks, turnstiles, barriers, electric drives, etc.). A particular type of locking device is determined on site or during the design process for large systems.
The second thing you should pay attention to is the identifier that will be used to access the facility (contact keys; contactless key fobs, cards; radio remote controls; biometric data (face recognition, fingerprints, etc.); license plates, tags).
Thirdly, it is software that can be used to manage, configure, generate various reports on the passage of access points, link to other security systems, and differentiate access rights.
Next, we select the equipment (readers, controllers, etc.) that needs to be used to solve your task.
Everything seems simple, but there are many nuances when calculating or designing an access control system. You need to consider whether it will be a control system or just an access restriction; how reliably you need to protect the object; you may need a payment system that differs from the access control system; and other issues. It is important that the system is sufficiently functional for you and your Object to which you restrict access or control.