The critical value of 0.5W is defined because in the field of amateur radio communications, it is generally believed that equipment below 0.5W has low output power, limited use distance, and is unlikely to cause interference to other equipment or radio and television. Therefore, these low-power devices are generally considered not to require approval and authorization, such as some small radio transceivers or kid walkie talkies.

In the United States, some unlicensed walkie-talkies include FRS (Family Radio Service) and GMRS (General Mobile Radio Service) radios, which have low power and limited frequency of use. According to the regulations of the US Federal Communications Commission (FCC), the power of FRS walkie-talkies must not exceed 0.5W, while the power of GMRS walkie-talkies can reach 5 watts, but it is necessary to apply to the FCC for a license to use. In addition, CB (Citizens Band) walkie-talkies do not require a license, but their frequency and power are limited.

The Amateur Radio Operator Certificate Exam is free. For example, in China, the test threshold for amateur radio station (category A) operating skills is very low. 30 questions are randomly selected from a question bank of more than 300 questions, and 25 questions are answered correctly to pass the test. These questions are public and can be consulted online.