How can I turn off my Time Capsule's wireless router?
Yes, using the Airport Utility you can turn off the router and WiFi functionality independently of each other.

Under the Wireless tab - Network Mode: select Off
Under the Network tab - Router Mode: select Off

At this point you can connect the Time Capsule to the wired network using the ports with a horizontal icon &lt;-> or even use it to receive the internet and connect your router to the ethernet ports. Bridge mode disables firewall, port forwarding, DHCP and DNS and makes it simply a network peer.