This is MichaelOh's Newbury Open Network in Boston, as installed at the Trident Bookstore... 
...using a 3Com® EthernetClientBridge to connect wirelessly to the Newbury Open Networkgateway.
This configuration can get its data via the AirPort's built in modem, or via an ethernet cable, or wirelessly.
(pictures not to scale)
Here are JonSchull's assembly instructions for a wifibox-esque unit 
-- JonSchull