The Dry Contact Unit provides interface flexibility to the controls engineer for indoor unit operation. The Dry Contact Unit is designed to enable or disable normal indoor unit operations or determine occupancy for setback temperature setting through a binary input. A binary output indicates if a system malfunction occurred. A field supplied binary signal could be taken from a building automation system, timer, keycard switch, door switch, motion detector or any occupancy, or condition sensor. The Dry Contact Unit can also be used to start/stop other occupancy related devices such as exhaust fans, fresh air dampers and fans, economizers, or lighting.