There are three kinds of air defense alarm signals: early warning, air raid alarm and disarming alarm. The warning signal sounds for 36 seconds, stops for 24 seconds, and repeats three times as a cycle, with a time of 3 minutes. What are the characteristics? Long interval? . The air raid alarm signal sounds for 6 seconds, stops for 6 seconds, and repeats 15 times for 3 minutes. What are the characteristics? Short interval? . The alarm signal will sound continuously for 3 minutes. What are the characteristics? No interval? . At ordinary times, we should try to sound the air defense alarm, so that everyone can be familiar with the signal of the air defense alarm. Once we meet the enemy, everyone knows what to do.