A facility code functions as a unique numerical identifier for an organization or specific location within an access control system. This code is programmed into security credentials, such as access cards or key fobs, serving as a digital signature that designates the ownership of the credential. By including this identifier, organizations can effectively silo or isolate their data and access privileges from other entities, even those using similar security hardware.
Defining the Facility Code
The facility code is a fixed numerical identifier assigned to a specific site or organization utilizing an access control system. The number is typically chosen by the organization itself or assigned by the manufacturer to ensure uniqueness. This site-specific number is identical across every authorized credential issued to personnel at that location. The code prevents cards from one organization from being mistakenly or maliciously accepted by another organization’s system, even if the individual card numbers overlap.
Technical Standards and Encoding Formats
The facility code is physically embedded into the electronic data string of an access credential according to established technical standards, most commonly the Wiegand format. In the widely adopted 26-bit standard, the total data transmitted by the card is broken down into specific fields. The facility code occupies a fixed set of 8 bits within this 26-bit string, which limits the possible facility code values to a range between 0 and 255. This 8-bit segment is distinct from the 16 bits reserved for the individual credential number.
Higher-capacity formats, such as the 37-bit Wiegand standard, allocate a greater number of bits to the facility code, significantly expanding the range of possible site identifiers. For instance, some 37-bit formats dedicate 16 bits to the facility code, allowing for up to 65,535 unique codes. Increasing the bit length provides a much larger pool of unique identifiers. The encoding format dictates the precise position and length of the facility code within the overall data structure transmitted by the credential reader.
Operational Role in Access Control Systems
In a physical access control system, the facility code serves as the initial layer of authentication for a credential presented to a reader. When a card is held near the reader, the complete data string, including both the facility code and the credential number, is transmitted to the access control panel. The system’s controller is programmed to recognize and expect a specific facility code unique to its installation site.
The system’s logic first checks the facility code embedded in the card against the code stored in its database. If the two codes do not match, the system immediately rejects the credential and denies access, regardless of the validity of the user’s individual credential number. This mechanism creates a security zone, ensuring that only credentials specifically issued for that site can proceed to the next step of assessing individual user permissions.
Facility Code vs. Credential Number
The facility code and the credential number serve distinct purposes within the security system. The facility code is a static identifier shared by every authorized cardholder at a specific site, making it a group or location-based parameter. It is fixed once established and remains the same for all cards associated with that facility, representing the “street address” for the set of credentials.
Conversely, the credential number, also known as the card serial number or cardholder ID, is a sequential and unique number assigned to an individual user. This number acts as the personal identifier, analogous to an “apartment number” within the larger street address. While the facility code authenticates the card’s origin to the site, the credential number links the card to a specific person’s access rights and permissions within the system’s database.