| 摘要 |
PROBLEM TO BE SOLVED: To enhance security without using radio waves, maintaining a mechanism whereby ID codes are checked electronically. SOLUTION: When an unlocking key 9 having a liquid crystal element 19 built therein is inserted into the cylinder lock 6 of a door body 1, the liquid crystal element 19 operates in accordance with an ID code (memory code) built into the IC chip 17 of the key 9. A signal of an LED 21 which is caused to emit light by a drive circuit 22 is converted by the liquid crystal element 19 into modulated light, which is then received by a photodiode 23. The modulated signal received is amplified by an amplifier 24 and checked by a decoder circuit 25. An ID code which is a characteristic of the key is stored in the decoder circuit 25 and, if the checking indicates that the ID code of the received signal coincides with the ID code stored, a signal is output from the decoder circuit 9 so that an FET switch 26 is turned on.
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