A data identifying system for identifying information recorded in a recording medium comprises: a discriminable card like a credit card having a magnetic stripe; a memory medium like an optical ROM card having an accident card list in which data regarding invalid cards (accident cards) is stored; a first reading unit to read the data stored in the memory medium; a discriminating circuit to discriminate whether the card is invalid or not on the basis of an output of the reading unit; a circuit to inform the fact that the card is invalid when it is decided to be invalid; and a second reading unit to read the data recorded on the card.

A check processing device incorporated in a point of sale terminal comprises a xerographic copier to reproduce an image of personal identification onto the back of a check, an electronic stamping mechanism for imprinting a transaction date, time and number on the back of the check and a scanner which reads and stores a customer's checking account number and controls a cash register according to the validity and presence of the check and the presence of personal identification.

A check or other document verification method in which a data encryption algorithm is applied to personal identification number (PIN) and selected other information particular to each document such as check number or amount of check. The resulting derivation is printed on the face of the document at the time the document is originated, in human readable form and possibly in machine readable form. The recipient of the document is issued a proprietary card, preferably an integrated circuit or "smart card", which contains an identical algorithm to that used when the document was originated. When the document holder presents a check for cashing or otherwise presents a document for verification, the cardholder is first identified with the card by inserting the card in a terminal and manually entering a PIN as is a common practice. Then the person who was given the document for validation, such as a check cashier, enters the selected information from the face of the document, which is processed utilizing the previously entered PIN and the algorithm from the card to derive a number. The number thus derived may be compared to the derivation which was printed on the document, visually or automatically by incorporating the capability within the terminal for reading the derived number from the face of the document. The proposed method thus validates the cardholder as the legitimate holder of the card, the cardholder as the legitimate holder of the document, and the document as having been legitimately produced for the specific cardholder.

An IC card is placed on a card terminal main body, and an internal IC of the IC card is electrically connected to an electrical circuit in a terminal through a connector. Input data entered by a card holder at a keyboard and data read out from the IC card are encrypted in accordance with a predetermined encryption algorithm and are compared with each other. Authenticity of the card terminal and the IC card is determined in accordance with the comparison result.

A point of sale printer includes a magnetic reader for processing transactions and payment by check at a checkout point of a retail establishment. The printer includes a magnetic or MICR reader located at a predetermined point on the printer's document travel path and a print head located at the same point on the document travel path but laterally offset from the MICR reader to allow the printer to print customer receipts and a journal as well as reading MICR information from checks and endorsing the check after it is cleared. A pressure pad is used with the magnetic read head of the MICR reader which utilizes a pressure film which flexes when a document is inserted between the magnetic read head and the pressure film to provide a spring loading force on the magnetic read head while still allowing the document to be moved smoothly past the magnetic read head. A method for processing checks using the printer utilizes bidirectional motion of the check along the document travel path to magnetize the MICR information, read the MICR information and print the endorsement on the check.