This paper explores the different types of biometric systems used in access control systems, focusing on fingerprint, hand geometry, and iris recognition. It delves into the techniques and technologies employed by each system, highlighting their advantages and disadvantages. The paper also provides real-world examples of how each biometric system can be applied. Furthermore, it examines three privacy-enhancing technologies (PETs) used on the internet, including data minimization, data tracking, and anonymity, illustrating their functionalities with relevant examples.