Whistle

A necessary emergency tool, portable and reliable. When a whistle is blown, it can be heard within one or two kilometers. Whether in day or night, a whistle could easily attract the attention of others.

Methods of using a whistle:  when calling for help, blow six times within one minute with obvious intervals. After blowing for one minute, stop for one minute to see if there is any response; if you hear someone blow a whistle and want to respond, you could blow three times within one minute, and then search for the place of the accident.