Restricted area security limits entry to defined zones and records who went in. It combines readers, door hardware, interlocking rules and video, so entry needs a valid credential while leaving stays possible. The point is not one barrier but a chain of them.
A restricted area is a decision about consequence. The stricter the zone, the more the design depends on procedure as much as hardware.
Control at the boundary
Each boundary needs a reader, a lock that suits the risk and a means of free egress. Two-person rules and interlocking doors reduce tailgating, which is the common way a credential system is defeated.
Evidence after the fact
A useful audit trail records who asked, where, when and whether the door opened. Pair it with camera coverage of the threshold, since the log proves a card was used, not who used it.
Related:Glossary: Access control systemIndustrial security systems