The KT-200 Door Controller is the basis of a 2-door access control system. The KT-200 is capable of controlling two separate doors or a single door (with readers on each side of the door). To form the system, each KT-200 is linked to other KT-200s using an "RS-485" communication bus. A smaller initial system can grow to secure hundreds of doors just by adding more controllers and the appropriate software.