A method and apparatus for electrically connecting two substrates using resilient wire bundles captured in apertures of an interposer by a retention film. The supply line L5 is provided with a heat exchanger 53, and the absorbing liquid is circulated using the density difference between the absorbing liquid flowing before the heat exchanger 53 and the absorbing liquid flowing after the heat exchanger 53 as a driving force. The adjustable attenuator may be configured to be connected to the network and variably attenuate a signal received via the network before transmitting the signal to the trainline communication processor.