In view of the frequent maritime accidents at that time, it was often impossible to send out distress signals in time and organize rescue as quickly as possible, resulting in heavy casualties and property losses. 1908, the international radiotelegraph convention officially identified it as an international universal distress signal.
The combination of these three letters has no practical significance, just because its code "...-..." (three dots, three dashes and then three dots) is the easiest for the sender to send and the easiest for the receiver to identify. The light emitting mode is: short light-long light-short light.
Use cigarettes
Smoke can be used to attract attention during the day. The international distress signal is three columns of smoke. You should try to distinguish the color of the smoke from the surrounding background: if the background is light, use black smoke and vice versa.
If you add some green leaves, moss or water to the fire, the smoke will turn white; If you add some rubber, rags soaked in oil, etc. On the fire, the smoke will be black.
In desert areas, smoke can't rise, and it always lingers on the ground, but in empty desert areas, pilots can still see it.
Using smoke as a signal is usually only suitable for relatively sunny days. Strong winds, rain and snow will disperse the smoke and reduce the possibility of your being found.
Smoke bomb. If you have smoke bombs, you can use them like flames. Grenade must be kept dry and effective when necessary, and be careful not to ignite the surrounding plants and grass when using it.
The above contents refer to:
Baidu encyclopedia -sos