Pepwave PDX slot Ports

Equipment : Pepwave PDX

Can someone tell me what is the purpose of the 3 rj45 slot ports located on the left of the WAN ports ? What are they used for ? I looked for some info in the device datasheets, but i didn’t find anything useful.

The PDX has 3 module bays on the left. These can be used for batteries or additional routers to increase the amount of cellular connectivity. In each module bay there is a patch lead to plug into the ‘LAN’ port of the router module. Those patch leads are then presented to the left of the WAN ports.

Thank you for your help Martin.