The Auxiliary Communications Service (ACS) was organized by the San Francisco Office of Emergency Services (OES) following the 1989 Loma Prieta Earthquake to support the communications needs of the City and County of San Francisco when responding to emergencies and special events.

The Auxiliary Communications Service holds its General Meetings on the third Tuesday of each month at the San Francisco Emergency Operations Center, 1011 Turk Street (between Gough Street and Laguna Street), from 1900 hours to 2100 hours local time. All interested persons are welcome to attend.

For more information, please attend an ACS meeting, check in on a radio net, or call 415-558-2717.

What is the Outdoor Public Warning System for?

The City’s Outdoor Public Warning System is designed to alert residents and visitors of San Francisco about possible danger. Specific emergency announcements can be broadcast over any one (or more) of the 109 sirens which are located on poles and on top of buildings throughout all neighborhoods in San Francisco, Treasure Island, and Yerba Buena.

Why do the sirens go off every Tuesday?

They are tested at noon every Tuesday. During the weekly test, the siren emits a single 15 second alert tone, similar to an emergency vehicle siren. In the event of a disaster, the 15 second alert tone will sound repeatedly for 5 minutes

What if I hear the siren at another time?

If you hear the siren at a time other than its regular test on Tuesday at noon:

  • Stop what you are doing.
  • Stay calm.
  • Listen for possible voice announcements.
  • Turn on the radio or television, (such as KCBS 740AM, KQED 88.5 FM) for important information provided by the City.
  • Avoid using the telephone. Do not call 9-1-1, unless you have a life-threatening emergency.

On rare occasion, special tests are done on other than Tuesday at noon - we will make every effort to inform the public of the date and time before these tests occur.