A user profile having consent information regarding a network server for a second party is created. The data includes a transmission ID, a calculated value and a reference value. An elimination device eliminates the extreme results of these indications and an estimation device supplyies a valid indication from the non-eliminated indications. The offset components contained in the differential input voltage signals are adjusted with the offset adjusting currents, and differential output voltage signals in which the offset components are added to the differential input voltage signals are generated.