Registers – Systems controlled by data bearing records – Credit or identification card systems
Patent
1993-06-03
1994-10-11
Hajec, Donald
Registers
Systems controlled by data bearing records
Credit or identification card systems
235382, 380 23, 371 571, G06K 500, H04K 100, G06F 1100
Patent
active
053549759
ABSTRACT:
When a control section of a data carrier discriminates a command from a reader/writer, either one of two kinds of pseudo random signals is returned in accordance with a bit 0 or 1 of response data. When two autocorrelation values obtained by correlation arithmetic operations are simultaneously equal to or greater than a predetermined threshold value, the reader/writer determines that a communication has been executed with two or more data carriers, so that an error warning, an access stop, a retry, or the like is executed. The reader/writer compares the autocorrelation peak value obtained from the pseudo random signal from the data carrier with a threshold value. When it is equal to or greater than the threshold value, the reading operation is executed. In the reading operation of continuous data bits from the data carrier, the reader/writer selects the minimum value from among the autocorrelation peak values of the bits obtained by the correlation arithmetic operations and stores the selected minimum value. When the minimum memory value is smaller than a threshold value, it is determined that data could not correctly be read, so that an error is indicated.
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M. Darnell, "Non-Periodic Binary Signals With Good Autocorrelation Properties", International Conference on Control '91, vo. 1, Mar. 28, 1991, pp. 178-183.
Hayakawa Shin-ichi
Ishibashi Yoshihito
Matsumoto Masakatsu
Filipek Jeffrey R.
Hajec Donald
Tokimec Inc.
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