# Cannot Establish Com Port (serial port) Connection

- Verify that the COM port settings are correct on each device. This includes the data speed setting.
- Verify that the cables are the correct type (see Cable Diagrams : Installation Guide) and that they are properly seated in the proper connectors (see RTU Bottom View and Connectors Diagram). If available, try swapping with another cable.
- There are six LED's on the main circuit board. For each of the three ports there is an RX LED indicating receive activity and a TX LED indicating transmit activity. See Interior View Diagram (RTU))