Abstract: A system for controlling access to a secured building area can include a programmable logic controller that is used to interpret data encoded on cards presented to a card reader at a locked door. The logic controller has one processor for decoding input signals, and another processor for comparing decoded data with data in a database, for thus generating a door-unlock signal. The programmable logic controller determines the permissions associated with the data encoded on the card presented, and unlocks the door if such access is permitted. Ancillary systems are easily integrated into the control system due to the modularity of a programmable logic controller-based system. Fire alarm override, burglar alarm systems, and infant security systems may be integrated into the system disclosed.