In August 2016, Supreme Leader Kim Jong Un visited the Sunchon Chemical Complex in the mid-western part of the country to see the newly-built process for the production of acrylic paints.
When he entered the PLC control panel room, a scientist told him that they applied non-contact contactor to the PLC control device instead of AC contactor.
Then, the Supreme Leader instantly said that they must have used a solid-state relay.
The scientist was struck with wonder. In general, non-contact contactor was in wide use in the world, but its application was so diversified that it was difficult even for experts to know what kind of device was used if they failed to observe it carefully.
However, the Supreme Leader understood solid-state relay, the most advanced mode of non-contact contactor.
Looking round the acrylic acid synthesizing process, he asked officials of the complex about the thickness of a raw material tank and its working pressure and permissible pressure during operation.
Listening to their detailed figures, he said they were good enough to the surprise of the officials.
It was because some senior officials had asked about the use of the tank during inspection of the complex, but none of them was interested in the factor of its safety.
Looking at the Korean letters and numbers written on the samples of acrylic paints, he said it would advisable to mark them with international colour notation, and cited some instances.