A communication exchanger has a memory which memorizes a presence state table for all of users and a forwarding destination table for each of the users. This method further comprises receiving responses to these fractional information queries and comparing these responses to data available from within a computer network. The insert has an engaging face disposed against the outer edge surface and a reference surface adjacent the engaging face, where the reference surface lies in a second plane, and the adjoining surface is adjacent the engaging face of the at least one insert and the first and second planes being parallel to and offset from one another. A secondary bearing is determined for some road segments. The controller performs a feedback control of the first DC-DC converter such that input current or output current measured by the current-measuring device becomes a target current, and also performs a feedback control of the second DC-DC converter such that input voltage or output voltage measured by the voltage-measuring device becomes a target voltage. The supply reservoir is adapted to supply the liquid to the transfer vessels under gravity flow, and the liquid applied to said transfer vessels provides the downward force.