The four major types of door access control systems are:
1. Key-based Access Control System: This is the traditional method where access is granted using physical keys. It is simple and straightforward but lacks advanced security features.
2. Keypad Access Control System: In this system, users must enter a specific PIN or code on a keypad to gain access. It offers higher security than key-based systems as each user has a unique code.
3. Card-based Access Control System: Users are provided with access cards or key fobs that they need to present to a card reader to gain entry. These cards can be programmed individually, making it easy to manage access for different users.
4. Biometric Access Control System: This advanced system uses unique biological traits such as fingerprints, iris scans, or facial recognition to grant access. It provides a high level of security as biometric information is difficult to replicate or forge.