Brief introduction of fixed-line SMS

It is an indisputable fact that no one dares to underestimate the potential of the concept of short message, regardless of its short-term ups and downs. Investors are already familiar with the concept of SMS based on mobile phone, which is also the origin of the word "thumb family". But in recent days, we can often see a relatively unfamiliar concept-fixed-line SMS in stock review articles, such as e-SMS phone developed by Shen Xin Taifeng and fixed-line SMS chip developed by Shanghai Science and Technology. What are these?