Comtrol DeviceMaster LT User Manual page 122

Sending and Receiving Data (RS-485: 2-Wire)
122 - Troubleshooting and Technical Support
3. Right-click in both COM windows and remove the check mark for Receive.
Both COM ports show Ready on the status bar.
4. Right-click in ONE window and select the Receive option from the pop up.
DeviceMaster LT User Guide: 2000586 Rev. B