This small article explains the definition of ETD and ECD.

ETD stands for equipment terminal data, examples of ETDs are PCs, PDAs, Tables, Smart phones, HMI, etc. On those devices, that usually send the information, the TX represents an output and the RX represents an input.

ECD stands for equipment communication data, examples of ECDs are Modem, Conversors (RS232/RS485), etc. On those devices, that usually receives or follows the information, the TX represents an input and the RX represents and output.

Summary

 ETD --> TX (Out) RX (IN)
 ECD --> TX (In) RX (Out)