The simplified word "door" comes from cursive script. After the Eastern Jin Dynasty, many calligraphers, such as Wang Xizhi, Wang Xianzhi, Yan Zhenqing, etc., all wrote "door" in grass, as shown in Figure A. Therefore, cursive script developed into a simplified word "door" after the Tang Dynasty.
In the 1970s, with the application of microelectronics technology, electromagnetic locks, infrared locks, electromagnetic wave locks, electronic card locks, 800 fingerprint locks, retina locks and remote control locks appeared. These locks have higher safety performance than the mechanical structure.
Modern locks can also realize the program control of the system according to the set logical relationship in a specific system. Modern locks can be classified according to material, use, key, safety performance and structure.