A commercial interface is provide in each Internet access network for carrying out cashless payments. The apparatus determines the presenceabsence of a correlation between the time-series change in the average process time of the server belonging to the first tier and the time-series change in the average process time of the server belonging to the second tier. The timing of the three data signals can be collectively moved with respect to the clock signal. The first operational amplifier and the first control MOS transistor having higher current driving capabilities operate in the normal operation state. , and more preferably at least about 2000 BTU-inhr-ft2-\xb0 F.