The relay output unit is a control device used for automated control of aeration fans in the Crop-Protector™ system. The units are controlled via the Aeration Control software that uses moisture sensor data to determine when and for how long an aeration fan should run to optimize grain moisture content. Each unit has eight relays with the relay status of open or closed visible on the diodes. Every unit has an individual Modbus address and can be installed where the aeration fans have their power start/stop relays to minimize wiring. One relay will normally control all of the aeration fans for a single bin, allowing for up to eight bins to be controlled via a single relay box. The relay output unit can also be used to control head space ventilation fans, either directly or via a help-relay. Data output (via RS-485 Modbus) directly to a PLC is also available.