 Etherloop has been deployed by various internet service providers in areas where the loop length is very long or line quality is poor.Some Etherloop modems (those made by Elastic Networks) offer a "Central Office mode", in which two modems are connected back to back over a phone line and used as a LAN extension.An example of a situation where this would be done is to extend Ethernet to a building that is too far to reach with straight Ethernet.