For many people interested in Building Access Systems (BAS), the knowledge that comes with years of involvement in all stages of design and use is a very rare thing to encounter. Proxy keys, databases, door controllers, and cameras all sound so simple, but being able to effectively make them work together efficiently can be a challege. In order to shed some light on the subject, this article is here to further explain how a Door Controller works.
First, this device is a unit that exists on the inside of a building that acts as an interface between your access point and your database. Second, many companies offer this equipment and they all have a different name and abbreviation for it. I will use one of the more common one known as an Entry Control Unit, or ECU for brevity's sake. Third, well I really don't have a third point to make yet, but we shall get there.
For an ECU to perform its job, it must have a way to communicate with the individual attempting to access a door. This task is typically handled by a keypad for PIN code access, a Proximity Card Reader for touch-to-access abilities, or in some instances a biometric unit is used. Some situations may call for redundant use of several of these devices.
Once the user enters in their unique access information, a signal is sent to the door controller (ECU) to request access. Since these devices function as merely an interface, they must request authorization from a central database. These systems allow for storage of a large number of access codes, permissions, and parameters. These can come in many shapes and sizes and depending on network setup, they may not even be at the same location. This allows for the added bonus of remote site security monitoring from a central location.
If an ECU receives a response granting access, it will send an alarm to the door-locks to signal them to open for an interval of time. If the reply from the NOC comes back denying the request, the ECU ceases action and the door remains secure.
Since the door controller is not responsible for maintaining access permissions, in the event of a network outage, they typically have a single default security code hard-wired in to allow a technician to access the door for any repairs.
Without the inclusion of a Door Controller, many Building Access Systems would be renderred useless.