《Regulations for Amateur Radio Station Call Sign Management》
Article 3: The amateur radio call sign is an important identifier for amateur radio stations. All amateur radio transmitting stations must hold a call sign assigned by the relevant regulatory authority.
When operating a radio from a different location/guest station, the call sign should include "B +" followed by the operation code and "/". When operating on someone else's radio (guest station transmission), you can also directly use their radio's call sign.