A coupling device for coupling containers includes a body part having a fastening piece and a cam part on upper and lower parts thereof, and a planar coupling plate between the upper and lower parts. A firewall is located between a dispatcher and the server computer. When turned off, the body of the first device is pulled to a bias voltage, and a first leakage current flows between its body and the first switch terminal. Another aspect of the present invention is directed to a non-cylindrical graduated refractive index lens structure. The resolution process may involve caching information from each contacted intermediate node during the resolution process to request leads on the target node in the form of a list of closer nodes known to the intermediary node.