Smarter Access Control is a powerful, easy-to-use solutionfor businesses ranging from small shops to large commercial properties. The MR50 Single Reader Expansion Module is designed to add one extra reader to an Alarm.com door controller. Each ADC-AC-MR50 adds one reader port, two relay outputs, and two programmable inputs to the system. Connect the expansion module to the controller using a shielded, RS-485 twisted pair.