A solid electrolytic capacitor includes a capacitor element, an anode terminal, a cathode terminal, and an outer casing resin. The cellular radio system comprises a testing device which is a fixed part of the cellular radio system and operationally connected to a data network. In the off period, a pulse modulator generates a pulse signal having a duty ratio adjusted such that a hold detection voltage VsH output from the sample-and-hold circuit matches the detection voltage Vs.