As a young child attending school in my kindergarten year, I remember how we learned to crawl under our (school) desk, stand within a door opening or line up and walk in a single line when we heard an emergency alert siren. The siren would indicate an air raid, earthquake, fire or any other emergency.
Because of 9/11 in Oakland, every first Wednesday of the month at noon, 27 alert warning system sirens are tested. Most siren sites are located in city parks, fire stations, corporation yards, schools, utility areas, and open spaces.
Chip Johnson, a columnist for the SF chronicle wrote in his February 2003 column:
After 9/11, Oakland expanded Capability made us aware of the new alert system in place for the City of Oakland.
The sound is a steady signal. Initially, it will sound like a fire truck siren, then increase in pitch and sound a constant tone signal until the alert is complete. At the end of the 3- minute alert, the siren will shut down. During the shutdown, the siren will decrease in pitch for 20-30 seconds until it turns off.