Cisco 1605-R How To Use Manual page 48

Installing a WAN Interface Card in a Cisco 1720 Router or Cisco 1600 Series Router
Step 7
After installing the WAN interface card into the router, proceed to Chapter 3, "Connecting
WAN and Voice Interface Cards to a Network."
2-14 Cisco WAN Interface Cards Hardware Installation Guide
Note If any WAN interface card slot on the chassis is unoccupied, install a filler
panel to enable proper airflow.
If the router was previously running, reinstall the network interface cables and
turn ON power to the router.