How door access control works

Today’s access control systems and solutions are more robust than a traditional lock and key, offering better security and more features than ever before. However, this more advanced technology also has more components and processes to manage. Successful access control implementation requires a general understanding of the different hardware and software the system uses, as well as how it all works together.

Components of an access control system

When designing an access control system for business and commercial buildings, the security system plan should identify and outline the following components.


In a commercial access control system, an entry is an electrified or automatic opening or access point that needs to be restricted for security purposes. An entry can be more than just a door. Parking garage gates, turnstiles, and elevators can also be secured with access control.


These devices are installed at every access controlled entry. Access control readers receive input signals from user credentials, and then authenticate them via a wired or wireless connection to nearby ACUs.

Locking hardware

In order for entries to be secured with access control, they require some form of electronic commercial door locks to be installed. These can include electric strikes, magnetic locks, push bars, or other electrified hardware that can be triggered by the ACU.


The access control unit, or ACU, is the control panel for the system. The ACU makes all entry decisions by authorizing the credential data sent by the reader, and triggering an unlock action on the locking hardware. ACUs come in a variety of sizes to support different door densities, and many offer input and output ports to connect additional systems.


Access control software is where the entire system is configured and managed. System administrators will credential new users, adjust access permissions, add new entries, and set entry schedules via the access control software.


These are how users will gain access to the building or space. Credentials come in many different forms, including key cards or badges, key fobs, mobile apps, PIN codes, and biometrics. The best credentials are easy to use, unique to the individual, and encrypted for enhanced security.

There are five main steps to how access control systems work:

1. Authentication

In this first step, a user’s credentials and identity are verified. During authentication, a user presents their credential at the reader (key fob, RFID badge, key cards) or shows intent to unlock (tapping a button on their smartphone, waving their hand in front of a touchless reader). Once the reader picks up the credential signal, it sends the data to the ACU to determine whether the credential is valid.

2. Authorization

This second step involves determining whether the user has access to the entry. Permissions, entry schedules, credential types, 2FA, and system lockdowns are all factors that could affect the outcome of authorization. For example, if a credentialed user attempts to unlock a door outside of their scheduled access hours, they will not be authorized for entry.

3. Access

If the user is authenticated and authorized, they’ll be granted access during this third step. The ACU will communicate with the door locking hardware to trigger the unlocking action, either by interrupting power to electromagnetic fail-safe door locks, or by applying power to door strike fail-secure locks. Once the user enters, the locks will reset to their resting state until the next authorization is completed.

4. Manage

Access control management involves configuring entries, issuing and revoking user credentials, setting entry schedules, and enabling alerts for access events. Access control management can be a time-consuming process, especially for multi-site enterprises with thousands of users. A cloud-based access control platform can reduce the hassle of management by automatically syncing with user directory services, and by automating the alerts and processes across IoT-connected sites and devices.

5. Audit

As with any commercial building technology, it’s important to perform regular audits for compliance, security, and safety purposes. Administrators should be able to easily and quickly generate custom reports of entry activity from the access control system, which help teams ensure the system is functioning properly, as well as identify potential security vulnerabilities.