Abstract: The credit card information management system checks the creditability of a credit card intended to be used for purchase of goods or service by using the card information owned by member stores of credit companies. A host computer of the card management center outputs information regarding the validity or invalidity of a credit card of a customer member of a credit company as card information, a transmission facility wirelessly transmits digital data of the card information. A receiving facility of a member store receives radio signals of the card information and checks whether or not there is any missing of data. If any missing occurs, a transfer of the missed data is requested to the host computer.

Abstract: A level difference detecting circuit 9 and an integrating circuit 10 receive a digital image signal inputted from an image signal input terminal 1 and detect a magnitude during a constant level period in every field. A determining circuit 12 determines the magnitude of the detected noise and selects the kind of a non-linear parameters to be used in a digital filter 8. Therefore, the digital filter 8 always performs processing for reducing noise by the most suitable non-linear parameter in accordance with the magnitude of noise.