Butterfly valves comprise a valve seat comprising a generally S-shaped cross-section and a valve seat retainer configured with appropriately shaped cooperating surfaces. The first display element is in an actuated state when a voltage difference between the first conduit and the second conduit has a magnitude greater than a first actuation voltage and is in a released state when the voltage difference has a magnitude less than a first release voltage. The proxying server retrieves from a remote server in response to a request from the client a Web document used to generate a Web page on a television screen coupled to the client. Other aspects, embodiments, and features are also claimed and described. Processes bound to one burb cannot communicate directly to processes and data objects bound to other burbs.