How to identify the types of air defense alarms

Today, 9.18. On a memorable day, air defense alarms are triggered in many cities. How many people can understand them?
According to national regulations, there are three types of air raid warning signals: pre-warning, air raid warning, and alarm relief.
Pre-warning: inform people in advance that the enemy is about to launch an air attack on the city, and ask them to prepare for the anti-air attack. It is required that the audio signal should be audible for 36 seconds and shut down for 24 seconds. Repeat three times for a Period of 3 minutes.
Air raid warning: It indicates that the enemy's air weapons are near the city, and the air strikes are about to or has started, warning people to hide quickly. It is required that the audio signal be audible for 6 seconds, halted for 6 seconds, and repeat for 15 times for a cycle, with a time of 3 minutes.
Release alert: indicates that the stage of the air attack has ended and the air raid alert has been lifted. It is required that the audio signal should sound for three minutes continuously.