Legal analysis: the numbers of police academy students are prefixed with Chinese characters or letters, such as "police academy", "criminal investigation", "X" (the pinyin abbreviation of police academy students), "S" (judicial) and "SF" (judicial). The alarm number is equivalent to the police's "identity card", with which law enforcement can be carried out. Normally, an alarm will follow a policeman until he retires. Due to the need of work and convenient use, multiple number plates can be allocated when distributing alarm signals. There are no letters on the official alarm, they are all numbers.
Legal basis: Article 36 of the People's Police Law of the People's Republic of China. The uniforms of the people's police are exclusively used by the people's police, and no other individual or organization may hold or use them. In violation of the regulations, the public security organ may, in addition to confiscating the illegally used standard clothing, detain or warn the perpetrator for less than 15 days, and may also impose a fine of less than five times the illegal income; If a crime is constituted, criminal responsibility shall be investigated according to law.