In a Mains Fed Echo Relay Panel (ERP) your EchoConnect connector is not labeled. EchoConnect is polarity dependent, so it is important to properly connect your stations.
If your ERP is top fed- your connector will start with positive beginning on the left side of the connector. Refer to the picture below:
If your ERP is bottom fed- your connector will start with negative beginning on the left side of the connector, essentially flipping the order.