A network routing device has a timing unit that sets times for issuing a network information update message to one or more other routing devices in the network. The islands are surrounded by an insulator. A plurality of frames is arranged between the first substrate and the second substrate to form an inner vacuum space. Thus, a subscriber can tune to a particular channel to play back selected content and be apprised, via receipt of the message over the particular channel, of a corresponding condition such as an emergency.