Brief introduction of four telephones

"Hu Si" is a term in the traditional linguistics of China. Phonologists divide vowels into two categories: open and closed, and each category is divided into overtones and consonants. The opening sound is called "opening sound", the opening sound is called "discharging sound", the closing sound is called "closing sound" and the closing sound is called "pinching sound".

The four calls in modern Chinese are related to the equal calls in middle Chinese. Generally speaking, the title of the opening corresponds to the opening of the Middle Ages. Ending the call corresponds to ending one or ending two; Tooth row call corresponds to opening two, three, four and so on. Wearing a green hat corresponds to closing three levels and four levels.