Security system and lock

摘要

A code system comprising a temperature-resistance conversion element the change of electric resistance value of which describes a hysteresis loop with respect to a temperature change; a means for changing the temperature of said temperature-resistance conversion element; a means for detecting the change of the electric resistance of said conversion element; and a time counting means of counting the actuation time of said temperature changing means. A hard lock device for use in the code system is also disclosed.