Report VFDs from Unitronics! One Solution for Control and Automation in Unitronics' Blog: PLCs, HMIs and more A group blog by Unitronics Home Team in General Posted August 8 Hi MIke, After we double checked it seems you are right. You need to connect a device on the Y1 or Relay output. Use Modbus 200BH, the corresponding signal can be output according to the setting value of Modbus. When it is set to 1, the output is ON, and when it is set to 0, the output is OFF. In this case, it's a way to send a virtual signal to Y1 or Relay output.