The ROS-MD-D04 is the third part of a highly advanced line of expansion modules. This unit works seamlessly with Rosslares state-of-the-art AC-425 networked access controller. Ideal for residential and commercial applications, the MD-D04 expansion board packs features such as advanced communication with the controller.The MD-D04 expansion increases flexibility to the access control system by adding four readers, four doors, four relay outputs and four supervised inputs to the controller. Left over from a closed business. Opened the box to check contents. All details in the pictures.