Facility code is also called as Site code, is a specific code that restricts or isolates other systems that might have a similar range of Badge ID’s access to specific site.
Consider the two sites belonging to same facility, and as a general standard, cards can be of any format but bit width is limited to 26 or 32. Let us assume a 26 bit card. Once the cards are issued to tenants, the serial numbers start from 0 to 65,535 and if the same 26 bit card is used at other site, again the tenants of that site will have cards starting from 0 to 65,535. It means two tenants will have same serial number and it will create a huge confusion as either of the tenant can enter any site hence will create huge impact on security.
In order to restrict tenants for specific site, the site code is added as prefix code for each site.
The example of site or facility code is as below
Site / Facility code
1 ~ 17000
1 ~ 17000
This way the cards are combination of site code & serial numbers, the site code acts as restriction digit.