PURPOSE: To prevent the surreptious use of a proper code number by a third person, by carrying out the writing and reading out in and out of a storage element by means of the same modulating and demodulating codes.
CONSTITUTION: An input data 1 comprising a proper registrated code number and a check word and an output signal of a modulating code generator 4 which generates a modulating code corresponding to said check word are fed to an exclusive OR circuit 3 with each bit. Thus a modulated signal 2 is obtained. This signal 2 is written into a nonvolatile storage element. Then a modulated signal 5 read out of a storage element to which a proper code number is written and an output signal of a demodulating code generator 8 are fed to an exclusive OR circuit 7 with each bit. Thus an output data 6 including a check word and a proper code number is obtained. The output of the generator 8 is equal to that of the generator 4. On the other hand, the data 6 is transferred to a check word deciding device 9 to have the discrimination whether or not the written check word corresponds correctly to the demodulated code.
TANAKA TAKEYA
YABE TOSHIHIRO
HANAWA TETSUYA
