Yes, this replaces the wifi portion of your AT&T network. You just use your AT&T modem for the incoming Internet and plug in the Google wireless device into your modem so it can broadcast the wireless signal. The TV boxes and other devices will need be set to recognize the correct network and password information that you use when you set up your new Google system. If you disable your AT&T wireless network, you can just set up your Google wifi with the exact same network name and password information, so all of your devices should be able to connect without changing all of their settings. Otherwise, just create a new network ID and password and then go to each of your TV boxes/computers and set up the new wireless connection information for the appropriate new wifi network.