The present invention relates to an electrolyte for the electrochemical deposition of palladium or palladium alloys on metallic or conductive substrates. The communication test device accumulates trace data on a specific unit of data complying with a designated communication standard, and throughput data on throughput of the specific unit of data transmitted to and received from a mobile communication terminal. The signal transmission line includes an insulating substrate whose one surface has at least one signal line longitudinally extending from one to the other end of the insulating substrate; and two net-like conductive layers laid on the opposite surfaces of the insulating substrate, the spaces for each of the net-like conductive layers being formed at random.