Access control, at its most basic level, is a system that can either enable or prevent people from entering or exiting a location. This can be applied to a single room, or across a whole site. 

A secondary function of access control may be to record the movements of building users in and out of locations. The data trails provided can be used for audit, traceability, improvement or compliance purposes. 

The majority of access control systems rely on the person or asset transiting in or out of a location being recognised and validated. This is normally achieved through the use of a “credential.” 

A credential can be broken down into three categories: 

• Key Card Identification Tag Smartphone App 

• Password PIN 

• Biometric data, such as: Fingerprints，Iris recognition 

In some systems, multiple layers of credential may be required.This is dependent on the requirements of the system, as identified in the specification process. Some systems may require a second-party credential. This can include a second keyholder, or recognition by an approved inspector via a CCTV link. 

As the number of layers and sub-systems increase, so does the complexity of integrating the system, and storing, accessing and making use of the data. 

Despite the flexible nature of access control systems, the objectives are often the same: 

• To protect building users from unauthorised access, which may threaten their personal safety or their possessions. 

• To ensure building owners meet their statutory duty of care and other legal responsibilities, including health and safety compliance. 

• To ensure the security of a building is versatile enough to efficiently manage the requirements of different users with varying levels of access.